2007 Dodge Durango 4X4 4.7 V8 - Trouble Code C1008 Brake Fluid Level Sensor circ

Hello, I live in Northwest Ohio and have a very clean garage kept 2007 Dodge Durango that I am working on. I am trying to troubleshoot a C1008 Brake fluid level sensor circuit too high trouble code. This vehicle came to me and the owner of the vehicle has replaced parts trying to get rid of his brake light on the dash. It says that the code sets when the brake fluid level sensor reads 4.9 Volts or more for more than 5 seconds. The odd part is when I measure voltage with my DVOM I only read 4.8 Volts and that corresponds with the Brake Fluid Level Sensor (V) PID on my Solus Ultra scan tool. I've done voltage drops on the ground side (.5mv) and Reference side (4.8V) from the brake fluid level sensor to the ground and the Front control Module. I've also done resistance checks of the wires and both had .3 ohms. The level sensor itself has 9.9 Kilo Ohms of resistance when Open and when i use a magnet i can get it to close and get .3 ohms resistance. I am able to watch my scan tool with my sensor plugged in and can use a magnet to close the circuit and the cicuit will close and read "low" on the PID. I can also use a screwdriver to push the float inside the resevoir down and the voltage will go to ground and indicate a "low" fluid reading on the scan tool. The owner requested that we gamble and throw a used Front control module at it and that didn't change anything.

He has also replaced...... (before bringing it to me)

The brake fluid level sensor.
The master Cylinder with reservoir that included another new fluid level sensor.
The brake booster (had brake fluid in it).

I am not sure what else to test, I was wondering if anyone had experienced this issue or had any advice on where to look next.

Thanks in advance,

Rick

how is pin fitment? abs light on??

I don't have the correct tools to test the pin drag. But i know the information is making it all the way to my DLC because when I unplug the sensor my voltage reading on my scan tool goes from 4.8 volts to 5 volts so i would assume the pins are making a good connection both at the sensor and at the front control module. The ABS light is not on.

After doing a little more digging on this system and reaching out to a friend that works at a Chrysler dealership I am finding out that there is another module of some sort in between the FCM and the Instrument cluster. I left the description and operation paper at my work so I can't remember what the Module was called and Alldatapro doesn't even speak of it and doesn't even offer an electrical diagram for it so my info is extremely limited and i am having to depend on a friend to try and use his dealer program to provide me information. But from what i recall it is a module that takes the info from the FCM and tells the instrument cluster to set the brake light on and set a code. The C1008 code is being set in the FCM module not the ABS module.

I've been trying to find this sensor and the FCM on the BBB Industries database, no luck yet. If you can post that description and operation, I'd love it see it!

Do you have access to a variable resistor? Mostly, I'm interested to know what voltage on the signal wire will make the FCM happy. 2.5V? Not sure exactly, just a guess.

I found this part at my local Radio Shack , and works perfectly for substitution testing. Try hooking the resistor up, start at 10K ohms (which is about what the level sensor reads anyway) and dial it down until the level PID reads OK. You can also use your multimeter to double check voltage drops, AND that the FCM is seeing the same voltage that you are at the level sensor.

If you can shut the FCM up with a variable resistor, then I'd think that there's still something wrong with the level sensors that have been installed already. Are there part options based on trim packages?

When I get to work Monday I will post description and operation. I did forget to mention that I did put a resistor in place of the sensor and was able to make the FCM happy and the brake fluid level read normal on my scan tool and codes cleared. That would be my last option as to a "fix" though. I would like to get to the bottom of this and fix it right.

W8up4Rick wrote: When I get to work Monday I will post description and operation. I did forget to mention that I did put a resistor in place of the sensor and was able to make the FCM happy and the brake fluid level read normal on my scan tool and codes cleared. That would be my last option as to a "fix" though. I would like to get to the bottom of this and fix it right.

Agreed, wiring a resistor in permanently would be the last resort. But at least we know the FCM can be satisfied! Just curious, do you recall what the voltage was that indicated an OK fluid level?

Where did the owner get the replacement parts from? Wondering if an OE sensor is in order, if one hasn't been tried already. You could even try measuring its resistance before installing it, see if it's lower than the 9.9K ohms you found previously.

The customer was using aftermarket parts. The sensor alone was from RockAuto.com and when that didnt work he replaced the brake booster, master cylinder, and resevoir w/ sensor as one unit from Autozone.

When I use the battery load test function on my DVOM any voltage reading between .5 volts and 4 volts makes the FCM indicate a "normal" level. The sensor is just and open/ closed hall effect switch. When the fluid get low the float in the resevoir must have a magnet that pull the circuit to ground indicating "low" fluid. And when the float is up (brake fluid full) then the circuit has ref. Voltage. So it's not like a variable resistor or anything.

I've been following this since you posted it as it's an interesting case study. I searched around a bit the other day but didn't find anything concrete so I didn't post. I hope that I'm not posting the obvious but thought I'd share my observations. I found the following diagram at the BBB database:

www.revbase.com/BBBMotor/Wd/DownloadPdf?id=139274



Page 1 shows the fluid level sense circuit. I couldn't find anything more specific about the FCM. At first glance the level circuit appears very simple. It looks like an open/closed switch connected to the FCM. However, if the circuit is monitored then I figured that couldn't be the case. I searched around for a FSM for the 07 but was only able to find one for an 04. In browsing that manual it shows this same circuit (but with the sense line connected directly to the ABS module instead of an FCM) but with a small added detail. Inside the sensor is a resistor. See below:



This makes sense (no pun intended) if the circuit is going to be monitored. It also explains the resistance of 9.9 kohms you are seeing across the sensor terminals, as well as the code setting criteria of seeing over 4.9 volts 5 seconds. Obviously, it has to see less than 4.9 volts and it's likely sending the 5v reference across that circuit for monitoring. There is a troubleshooting tree in the 04 manual and while it doesn't mention what the resistance spec should be, it does say that if it's over 11kohms that the sensor should be replaced. Seems to me if you have any corrosion or other problem in the sensor connector pins, at the ground (G114), or even at the FCM, or possibly at the TIPM, you could get the code you're getting. Since the code is being set by the FCM it makes me not suspect the TIPM. Can you get a resistance reading from between the FCM, at the sense line, through the sensor, and G114?

I will check total circuit resistance. I know that the sensor signal wire between the sensor and the FCM reads .3 ohms. And the ground wire coming off the sensor to g114 reads .3 ohms as well.

Man, John schooled me on finding diagrams with BBB. :lol: :blush:

Spent better part of 2 days doing point to point wiring checks on my 2007 Durango with 5.7 and constant Brake light on dash. Had replaced the master cylinder with a new Cardone master cylinder (made in China) and finally found after using my Fluke meter that the old sensor gives 2,000 ohm when full and the new sensor from Cardone gives 10,000 ohm when full. Finally swapped the old for the new sensor and it works as expected.

Seems the circuit requires a small bit of current to go through to ensure everything is connected. This worked for me and hope to save someone else some time.

[quote="billb" post=22121...Seems the circuit requires a small bit of current to go through to ensure everything is connected. This worked for me and hope to save someone else some time.[/quote]

That means that there is, indeed, a resistor in the sensor and it's not just an open/closed sensor.