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Mr Paul Danner and Assorted Experts - Retired Vietnam vet here trying to help my son. I have thoroughly enjoyed and learned from Premium for the past months. 2004 Grand Cherokee quit with no warning - drove home from work, shut off normally, quit dead. Cranks but won't start. Never any indication of ignition. Brand new battery fully charged. We have pulled every fuse and relay inside and out. Unplugged Crank Pos. Sensor. Tried a second PCM. The consensus is a shorted sensor or wire "stepping on" 5V reference. I have seen Mr Danner unplug many sensors in several videos to find fault and restore 5V reference. My VOM on pin 2 of DLC shows a fluctuating voltage of between .8 and 1.35 volts no matter what we've tried.
2004 Jeep GC 143,000 miles 4x4 Auto 4.0 inline six. Truck has been reliable for several years with no electrical issues. I am unable to read any codes because of NO COMM.
Simple question ladies and gentlemen: How many sensors have to be pulled and where located? Connectors are intimidating to me frankly.
Any comment/help greatly appreciated. For the money, Danner Premium is unbeatable. Please continue the great work. Thanks Tron Duick
I will be at the truck on Monday and will pull and check all sensors in Ben's very helpful wiring diagram. No, I didn't check for 5V at crank position sensor or any other. The pin 2 voltage I did check wasn't at PCM - it was at DLC. I had battery voltage 12V at PCM and I am not competent to know how to check ground - but the ground voltage to PCM was under 1V if I remember right.
I will try to answer all questions and shed as much light as possible. This is a very challenging field for a beginner!
I followed Ben's diagram and disconnected the four sensors. I plugged scanner into DLC and turned key on. Communication was immediately established with VPW bus and the instrument panel was restored to sanity, with MIL working properly and SKIM light off. Fuel gauge worked OK. With all sensors unplugged, a single DTC P0123 TPS "Circuit High Input" was set. It reset on plugging sensors back in, and reported no codes whatsoever. I guess my takeaway so far is that a faulty or shorted CPS sets no code because it steps on the bus. But my understanding is poor.
Anyway I plugged sensors back in first TPS second MAP third CamPS and finally the infamous Crank Position Sensor. And in fact it is the CPS "stepping on" the 5V reference. It is a reproducible error. It's amazing to do in person what I've watched Mr Danner do in various videos, and have it work.
I bought a $46 "lifetime warranty" CPS from Advance and have it in hand. I accessed the CPS bolt through the transfer case cable hole in the firewall, from the passenger compartment; and was able to loosen the bolt. Today I will try to replace the sensor. There is no clearance anywhere -
It may be the case that 2004 GC is under recall for frayed wiring to CPS in the loom at the back of the engine. Given the tight fit, no surprise. I haven't had time to research it.
Many thanks, again.
The following user(s) said Thank You: ScannerDanner
Good to hear you got it figured out . Make sure the clearance pad is on the end of the CKP when you install it and have an assistant hold it down to the flywheel while you tighten it down, also these can be tightened down from underneath with a hand full of extensions and a swivel socket (I've never attempted it through the firewall)
I was able with a lot of finagling to get CPS tightened through firewall hole used by transfer case cable - I was working alone - it is purest misery to me anyway. I used a small hook in the end of a piece of 12-gauge bare copper wire around the three-wire bundle coming out of the CPS to pull it into place so the bolt could start. I also put a magnet into socket and used electrical tape around the bolt and around the universal to keep those stable. Kept paper spacer on. I wasn't able to get the guard in place so it's left off. I'll put some silicone caulk around the wire when it warms up in April.
I used bootlaces on both ends of CPS as a fishing aid, after reading a lot of forums. I think it would be nearly impossible to fish the harness around back of engine without. You have to tie laces to the old sensor first and then onto new one so you always have something in place. Of course we all fix things in our way and a bit differently. The old sensor looks like the OEM put on when truck was built.
The engine was running within a second and after sitting six months the Jeep ran faultlessly on the 300-mile trip home. Whew!
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