2003 Mercedes Benz c240. I Had a Circuit Malfunctioning

Walter Zafaralla
1496 Lehia Street
Honolulu, HI
(808) 772-4778
walter.zafaralla@gmail.com

Professor, Paul Danner
Rosedale Technical College
Pittsburgh, PA 15205
2/15/2022

My aunt gave a car to my twin sister year model 2003 Mercedes Benz c240 4 Matic. I am not sure why she gave away the car. Maybe the car it's old enough to depreciate in nearly two decades. Maybe she feels tired with her mechanic because the car problem kept coming back. Naturally, when we got the car, a/c not working, engine oil service interval exceeding 250 miles, interior right vanity mirror lamp not working, air temperature sensor reading up to (185°F), both mirror adjustment and exterior fog lamp dead too. For the moment we had the car was running okay. After two weeks of using the car, there was a problem in the window. The rear left power window glass got stock and did not rise all the way up. It is just a switch window regulator working going up and down. We still use the car even if the window does not work. Always arm and lock the car after we use it. Even if it's wrong to fully arm and lock the vehicle with a window glass open says in the repair manual. For what is known as “Control Unit Memory Savers” or vice versa a (EIS) Electronic Ignition Switch is known as the gateway that can transfer information to (PCM) Power Control Module and Automatic Transmission Control Module etc.

And then, the next day my sister used the car to pick up my younger sister at the airport. When they got home, the car had a problem. The engine cooling fan operates a high-speed signal. Check engine light appears in the cluster “Coolant Visit Workshop”. The fan is running all the time at max speed. So, I was called to look at the car with an engine problem. I cycled the key and turned the ignition off. There is a signal 1 Malfunction appeared in the cluster. I noticed that some portions of the lighting system were lost. Such as the auto headlight switch set 15 seconds delayed shut off no longer works. Also, interior lamps with an overhead switch set to 5 seconds delayed shut off are gone. Even after I unlock the vehicle, both the front and rear dome are no longer working.

As a result, I got the first trouble code P1007 Engine Coolant Temperature Sensor 1 Low Circuit with a battery voltage 12.6 fully charged.

Please help,
What is my next step?

Someone once said, "a free Mercedes is the most expensive car you'll ever own".
As for your question "What is my next step?", what problem are you trying to fix first?

Aloha , just a quick update to all. Basis thing i checked the car earlier and test if I have a bad ECT sensor itself. For less than 30 seconds I made car start. As soon as I unplugged the ECT sensor, while the car is idling my scanned data showed -40 degree Celsius and the engine cluster temperature gage displayed a coefficient value back down to zero degree Celsius. Seems okay to me that was no loose broken electrical connector going in the ECT unit. Maybe the sensor itself is faulty. Maybe I call Mercedes Benz of Honolulu and order an ECT sending unit. Maybe I could fix the fault code p0117 if the sensor is replace. 'll take a look again tomorrow. Maybe I'm wrong. Any advice?

Walter Zafaralla
1496 Lehia Street
Honolulu, HI
(808) 772-4778
walter.zafaralla@gmail.com

Professor, Paul Danner
Rosedale Technical College
Pittsburgh, PA 15205
2/16/2022

Another day of troubleshooting the P1007 ECT sensor 1 low circuit. I was not sure what to do first since yesterday. This morning I went to O'reilly auto parts to rent a scan tool. Unfortunately they don't have smart scan tools available. All they had was OBDII, a simple scan code reader to extract the trouble codes. As I couldn't find a one professional scanner to look for malfunction in the vehicle, I decided to go to the Mercedes Benz in Honolulu. I went to M-B of Honolulu this morning and bought an engine coolant temperature sensor. I was happy and confident that I could isolate if the sensor is replaced. I believe that the ECT sensor I got from the dealer it is new and it is the right part number for 2003 MB c240. I replaced the ECT sensor and erased the fault code. As a result, nothing has changed. The stored code P0017 ECT sensor 1 low circuit did not illuminates and still there is a malfunction in the engine cooling fan. The PCM does not want to be reset and check engine light stays "Coolant Visit Workshop". Consequently, I was made a bad call today. Earlier I should be check my 5 volt ref and signal ground to verify that I have circuit integrity.

However, this afternoon I work another way and it was signal circuit integrity test. Seeing that, circuit low trouble code (P0017) ECT sensor 1 low circuit. I made a jumper wire from a 5 volt reference wire and the other wire from signal ground. I disconnect the suspected faulty new ECT sensor. I jump my 5 volt ref to signal ground with key on and reread code. Subsequently, I have a circuit high trouble code (P0018) Engine Coolant Temperature sensor 1 circuit high. I would say my wiring is good. Nearby, I checked the coolant level and mixture is full good amount of mixture protection. Granted, my circuit integrity for ECT sensor is good. And, the PCM is good watching every move if I mess up. The PCM works properly and voltage and signal ground that comes out accurately calculates the data temperature in the engine coolant. So and so, I am not sure what to do with the P1007 ECT sensor 1 low circuit. Revealing that the input circuit on the ECT is shorted sensor or losing power and ground. The ECT sensor is new. I don't have enough evidence to assert that the ECT sensor is the main issue. Even a new ECT sensor from the dealer did not fix the problem. My blames pointed out to the dealer if their side is fault too. Thinking I might have bought a sensor manufactured defect. I consumed troubleshooting in that particular sensor and it did not fix the issues. PCM wants me to do some more detective work. I am looking forward.

Mahalo!!!

I think you're saying that the engine is not overheating.

You can do an ohm test on the ect. Ambient temp in Hawaii 68-77°, ect should ohm around 3520 to 2796 ohms. If you have low numbers say 177 ohms then the ect is bad.

Low voltage means high temp. The 5v is being pulled to ground. With jumper test showing high voltage that's indicative of good wiring and a bad ect. Note: Never ever stick anything in the female pins of any connector as you spread the pins and they loose contact with the male pins when reconnected. If you have to front probe, touch the pins lightly.

Disconnect the fans and see if the ect reports correctly. Possibly the fans are shorted and pulling the ect down.

Walter Zafaralla
1496 Lehia Street
Honolulu, HI
(808) 772-4778
walter.zafaralla@gmail.com

Professor, Paul Danner
Rosedale Technical College
Pittsburgh, PA 15205
2/19/2022

Because you told me a thermostat internal fault, so I spoke today with M-B of Honolulu to return the new ECT sensor under manufacture warranty. Sadly, cannot be return the unit item specifically electrical components and special order. So, I just ask the dealer politely what I should next, and the dealer told me I could take the car to them, and there they can test if the sensor defaulted. The problem is how do I take that car there because the ability to drive the car is not functioning properly. Unable to drive because of the malfunction situation causing to overheat the engine. I really feel the condition of the engine management control, such as the ignition timing and the idle speed are seriously looping and exhaust misfire. Anyway, I almost damned for blaming the dealer that is a faulty sensor but is not. I made a second measurement with the ECT sensor. What I saw was that my old sensor and the new one was just the same as resistant. The ECT sensor is active and have a correct amount of resistant. As stated in the Haynes Repair Manual, "The ECT sensor is a Negative Temp Coefficient (NTC) thermistor temperature sensitive variable resistor, the resistant of the thermistor decreases as the coolant temperature increases". In other words, the active resistant of the thermistor increases as the engine coolant temperature cold which exactly I did on the voltmeter that I took photos showing a resistant measurement. For that reason, the car issue is really big, different and is not a shorted ECT sensor. To me this is an indication of something going on with the engine computer tells as a not equally sharing a reference circuit design. Meanwhile, I always unplug the cooling fan when I do a voltage drop test on the P1007 ECT sensor reference 1 low circuit. I gently check the two wires in the ECT circuit with GRN/RD and BRN/WHT colors. The one that is my reference wire GRN/RD is 3.8 volts with a loaded circuit and 5.8 volt with unload circuit. Whereas my signal ground BRN/WHT is under 50 millivolts. Meaningful, I have a good 5-volt refs signal on the ground. My concern a short to ground, because my sensor ground wire is missing 100 millivolts in this leg of the circuit. A short to ground is my really concern which I need help of who has a better experience about a 5-volt reference 1 circuit.

Mahalo!

BRIEANNA138 wrote:

Unable to drive because of the malfunction situation causing to overheat the engine. I really feel the condition of the engine management control, such as the ignition timing and the idle speed are seriously looping and exhaust misfire.

Walter,

You had not mentioned that the engine was overheating previously . Monde asked,

Is the car overheating? A stuck closed thermostat would cause the p0117 code.

BRIEANNA138 wrote:

Because you told me a thermostat internal fault, so I spoke today with M-B of Honolulu to return the new ECT sensor under manufacture warranty.

scannerjohn said,

I think you're saying that the engine is not overheating. You can do an ohm test on the ect. Ambient temp in Hawaii 68-77°, ect should ohm around 3520 to 2796 ohms. If you have low numbers say 177 ohms then the ect is bad.

This would be a NTC sensor. As temp rises, resistance decreases. High voltage, 5v would be cold engine. 3.5v a hot engine. Your Ohm test of the cold sensor shows 2217 ohms... ambient temp that day must have been above 77. Testing before changing parts is what this forum is for. Your wiring integrity is good and your sensor readings within specs. This is not a sensor problem as you have found out. Had the forum known of the overheating we would have suggested other directions to explore and test. You mention "exhaust misfire" did you mean to say backfire in the exhaust? This would be different that a misfire.

A quick and easy test for the overheating, check the temp of the upper radiator hose. If its cool or warm when the engine is hot, the thermostat is not working correctly.

Let us know what you find, we all want to help you get your car back on the road.

Aloha,
I just want to clarify and explain whether I was wrong in saying the exhaust misfire. I mean engine misfire and the car might overheating if I take it to the Honolulu dealer which is 9.5 miles away from home. Especially the condition of car right now when I drive the vehicle @ 9.5 miles with a malfunction in the ECT and engine fan maybe the computer may stay in open loop and engine emission control will suffer.

I am little unclear when, " check the temperature of the upper radiator hose. If it is cool or warm when the engine is hot, the engine thermostat is not working properly".?

Do you mean when engine is reaching normal operating temperature the upper radiator hose is hot then thermostat would not perform properly...? What does a normal temperature in the lower and upper radiator hose when is fully warm up...? Or do you mean when an upper radiator hose is cold because the engine takes a long time to warm up, the thermostat is probably stuck open.

However, I looked at the car again last night because you told me to test thermostat for overheating. Granted, I started the car on idle. During warm up the engine stay in open loop. After three minutes later the engine is closed loop and the lower radiator hose is soft and cold and has a reading of 43 degrees Celius. While the upper radiator host is kind of hot with a little pressure and has a reading of 67-degree Celius. While, observing an engine thermostat when start to be activating and when it is fully open temperature, a watch timer it takes exactly 20 minutes to fully open the thermostat with engine coolant temperature 90–95-degree Celius. As a result, a radiator lower hose is hot 76-84 degrees Celsius and upper radiator hose is pretty hot reading with 84-86 degrees Celsius. To me this is a good thermostat control engine coolant temperature. As a mention above during warm up the thermostat possibly closed which lower radiator hose cold prior to prevent coolant from circulating through the radiator. As the engine reaching operating temperature, the thermostat job feel begins to open and allows a hot coolant to travel through lower and upper radiator hose. Although, the lower radiator hose supposed to be lowered than the upper hose by 10-degree Celius maybe because I have the fan unplugged. Where the engine fan automatically kicks on when the engine is hot a level temperature. Because cooling fan at maintaining the coolant temperature, can produce cooled before returning to the engine.

In this case assuming the thermostat is not probably causing a P1007 engine coolant temperature sensor circuit 1 low. The issues really need to be emphasized on a 5-volt ref short to ground. Causing engine fan malfunction and temperature gauge coolant visit workshop light on operation, which I think it is responsible for P1007 ECT sensor circuit low and other sensor high circuit.

Watler, I assumed you would know to check the radiator hoses when hot, sorry. I think we all can say that the thermostat is work.

I do not think I recall you saying if the temp gauge in the dash is working. Is it? What is it reading? After 20min at idle, if the engine coolant temp did not go over the 86 degree celsius mark with the fan unplugged, then overheating probably is not the issue.

BRIEANNA138 wrote:

In this case assuming the thermostat is not probably causing a P1007 engine coolant temperature sensor circuit 1 low. The issues really need to be emphasized on a 5-volt ref short to ground. Causing engine fan malfunction and temperature gauge coolant visit workshop light on operation, which I think it is responsible for P1007 ECT sensor circuit low and other sensor high circuit.

You did the wiring integrity test on the sensor, recall the by-pass test you did and you Ohm'd the sensor itself and both were good so I think you can move away from those for now.

I think Mercedes have a module for the fans... I believe your fan circuit that is setting off the P0117. You have posted P1007 along with P0117. They are two different problems. Are you getting a P1007 as well?

Let us know what you find.

Aloha, I have got the same temperature as showing in the dash and data. In 20 minutes the engine temperature hit up 90-95 degree celius which over 86 degree celius.

I always have to convert... that's 194 to 203 F... because you do not have a manual fan, I would expect the electric fan to kick on at that temp range. My Tahoe runs about 195F and does not have electric fans. Sorry don't know what Mercedes temp range to kick on fans... just to be clear, your fans are on from cold start to operating temp? If you're not going over the 90-95 with fans on you're still Ok.
Are you having problems with your AC... you mentioned it in the beginning. What problem or problems? The coolant control module controls the AC fans as well as the radiator fans.

Right, I also don't know a cooking type of this engine before engaging on cooling fan. Which is suck I recently purchased Haynes Repair Manual is very short of details and limited in the wiring diagram. This issues right know do not appear even mention at all in the manual, so I don't wanna guess where they subsequently connected. Somehow we can say approximately. For example, my X5 straight line six cylinder a normal range temperature engine before automatically on the a/c/auxiliary fan has 90-100 degree c which is equal to 200-210 f degree. Because the a/c also include a integral auxiliary fan, as long as the engine is reaching a operating temperature constantly work even if you don't touch it, then the clutch fan will engage as well.

By the way, yes the engine cooling fan forever at on once you turned the key. Then the a/c compressor dead does not work either.

BRIEANNA138 wrote:

By the way, yes the engine cooling fan forever at on once you turned the key. Then the a/c compressor dead does not work either.

I would look more at the fan module. 4 wires. 12v, ground, signal and ign 12v. That's an expensive part so don't fire that parts cannon. You might have to have someone test that for you. Because fan on all the time, suggests module has gone out. Notice I said " suggests". Test first before replacing.

air temperature sensor reading up to (185°F),

I would look at this, if this is interior temp the A/C will be commanded on - and so will the fans. If the A/C is not working the ECU them may make assumptions as to why relating to engine temp (or it may just stop the A/C unit from turning on). Also you can't always trust a basic scan tool to give you accurate code descriptions.
Also do you have plenty of coolant in the engine ?

Aloha,
I have uploaded a partial diagram for Electric Suction Fan Engine and A/C with integrated control. Early I checked the fan wiring control, and it is not the module fan assembly is the issues in my opinion. I don't like what I see on the number of control side. A fan control wire GRN/BLU coming directly from the PCM reading of 3 volts. The second supply control wire a BLK/BLU is the Evab purge solenoid valve with a reading of 3 volts as well. I expect to get a higher voltage of the green blue wire because my reference when I load the circuit engine cooling fan will take a draw amount of voltage amperage which can cause a low circuit 1. While the purge valve is fire up to 12 volts which is probably causing an even high circuit.

However, I want to go back to my prediction that maybe the engine computer is going bad with intermittent circuit codes. Consider what I can learn in the Mercedes Benz C-Class Automotive Repair Manual. Maybe the PCM will get better if I fix the window, A/C and air ambient temperature sensor. Maybe fixing these output and input component can be added to the engine management control module.

Awareness from Haynes Repair Manual Mercedes Benz Class 2001 through 2007, stated that The engine management system’s PCM has some learning capabilities that allow it to adapt or make corrections in response to small variations in the fuel system in order optimize drive ability and idle characteristics. However, the PCM must go through a relearning process before it can regain its former drivability and idle characteristics. Until it relearns this lost data, you might notice a difference in driveability, idle and automatic shift feel. Also said that, After voltage to power window modules has been interrupted the positions of the windows need to be resynchronized and keep the window fully closed. When the control module for the power window assembly detects a motor lock up, it sets the position recognition counter to zero (Chapter 5, section 1) of general information.
In other words, I'm worried about memory savers because the power window has been interrupted. Because of their electrical roll according to the manufacturing instruction. Might lose some information when the power window circuit does not function properly in its position. May have confused the Power Control Module by the EIS since the rear left window is recognizing open circuit. Maybe it is not synchronized to each location and applies to all four power windows. At the same time it is not good the fan is running all the time. It seems like something is happening in multiple circuit codes from the engine computer.

Maybe if the A/C and pressure of an air ambient temperature sensor does force the PCM to short. As a result, to malfunction the engine cooling system related to a low and high circuit code. Specifically, the PCM is commanding an incorrect climate atmosphere temperature (185°F ).

My point is If that's a correct temperature outside on any given day, almost like you put an egg in the desert, will cook or boil water point; For me without a lot of questions, just replace the engine PCM one time. Replace with a new engine computer $ 2,000 just to solve the variable circuit problem. To me that is kind of odd. Over-thinking should not be the case of this car. I think the PCM is on target for processing the correct data and output commands. I think the PCM knows the driving ability and body temperature. If I remember when unplugging the ECT connector, PCM receives data to calculate how much input and one circuit low from all of the input engine sensors. I tried to think well that PCM is communicating, not a problem.

May be elsewhere, tell me how to double check the power and ground on the PCM before we can continue to say that engine computer is a bad.

Mahalo!!

Located on the backside passenger side bumper near the fog light in the lower grill.

You can bench test sensor. Use ohm meter. Zero ohm is a bad sensor. Ohms change with heat and cold. Use hair blower to test sensor. Wiring is 5v and ground. Check for power and ground. Like the ECT you can do jumper test.

At $2k for an ECM I would do a lot more testing before spending that amount. Your time and labor is free.

Second of all, is to fix the power window and ambient temperature sensor. Before I began, I had disconnected the battery ground to avoid triggering an airbag. Removing the door panel trim, it's too easy, not like BMWs more difficult. With the door panel off unplug and remove the speaker from the door. It is held in place by three T20 torx screws. Around peel back the membrane with sticky stuff from the door. I leave the membrane halfway open so I can see what's broken from the window regulator. Left in the bottom the window slammed out and the regulator motor cable was holding the T40 screw and mm 10 mm nut. The window regulator clip is wrecked and falls apart into three pieces. I fixed the rear left window and put everything back in place.

Next too, is fixing the air ambient temperature sensor in the front. In front of the vehicle, I could not see an ambient sensor. I was thinking the down spot might have the ambient sensor just popped out and hung underneath the engine. I had to jack up the car and remove the tire and wheel liner. I had to push back the wheel arch trim just far enough so I could have a better shot and access. When I finished clearing out, I could not see an air ambient temperature sensor. Beneath the engine bumper I did not find a wire sensor for the ambient temperature. I said what!! Impossible that this ambient sensor does not exist in a Mercedes. To prove it I had to really remove the front bumper. As I removed the bumper the bolts, screws and pull push plastic pin are not the real parts together for a European car. Benz. Equally important to me is that European fasteners are a metric size pattern. Typically, when working with European front bumper fasteners are classified into sizes only. For example, 8mm screw,10 mm bolt and nut or T30 Torx bolt. Almost all of them find thread and lock washer fasteners. Part of the reason I'm saying this makes me peace off. I struggled to remove that pivot bracket sideways away from the bumper and fender screw. Has a small nut too and it is a hardware type screw it does not want to come loose? It is just spinning on me every time I try to unscrew. To the point I was running out of patience swearing working in the garage. The only thing that bothers my mind to continue and fix the car is what the idiot mechanic person did over. Why is the installation of the bumper so tangled, twisted and confusing, I even question myself if that demon mechanic person went to that location why there is a faulty vehicle ambient. There would have been the air ambient temperature fix or at least hanging, but none. If the demon mechanic person before did not install the car parts perfectly, screwed up maybe chose something he did wrong that caused the vehicle now to malfunction. I am looking forward to seeing what kind of job he did beside the bumper. I take the bumper cover off and disconnect the fog lamp electrical connectors. Further, I really do not see a sensor for the outside temperature gauge. The only thing left is a harness going down to the foglamp. Then, I noticed the fog lamp harness and things were out of place. Regardless, European car electrical zip ties are black, they are called the cable tie mounts umbrella push. I noticed that unusual tie color white used in the fog lamp harness where it was installed anywhere behind the bumper frame. I checked carefully the way fog lamp harness routing. Unwrapped the electrical tape of the fog lamp harness wire from bottom to top. While working in the right front corner of the fender, I was able to see a suspicious piece of stiff wiring to the end of the fog lamp harness. Trace the wiring back along the upper edge of the fender and pull that piece of stiff wiring tape. As a result, the harness for the fog lamp and outside temperature sensor were absolutely broken wire. The sending unit of the Ambient sensor and fog lamp was cut down and buried underneath the upper edge of the fender. Evidently, the devil mechanic removed the rest of the harness and sensor without regret.

Also, here is what I found after I dug more, the evil mechanic person cut the wiring ground. Right away guys the Chassi ground was cut where the engine fan and other fog lamps are grounded. I realized now as I'm doing this faulty engine coolant sensor, engine cooling fan malfunction, damage a/c, foglamp and ambient sensor are mess stuff for a long time. Nowadays, this makes me dig more and peace off. I'm sure this is related to having a blown fuse, low or high circuit break, short to ground, reference circuit problem, voltage problem or causing a faulty PCM.

what can I do even if the ambient and window of the car are fixed but there is still with a circuit codes and cooling fan malfunction? Can we say that the PCM is faulty?