Engine/Transmission (1998.5 - 2002) CPS failure symptoms?

[T Peterson]

You're right, pm sent.



Tom

 

[JLandry]

Here are the symptoms, start cold, drive for 4 to 6 minutes then tach dies and 2 seconds later I lose power (not limp mode I think, I can still go 70 or so but not uphill and very little acceleration) then 4 or 5 minutes and tach comes back, 2 seconds later power returns and all is fine until the next cold start.

Tom,



When this low-power event happens, does it happen every single time you operate the truck... or only occasionally?



Does the tachometer stay dead (which I assume means reading zero rpm) during the entire low-power event? If it does remain at zero, it seems to me like it's got to be a heat-related intermittent loss of the CPS signal to the ECM just as the trouble code indicates.



Did the mechanic carefully check the wiring harness, the CPS connector, and the appropriate ECM connector pins when the engine has been warmed to point where the low-power event occurs?



Thanks,



John L.

 

[JLandry]

Tom,



A couple more questions:



Does your truck have an automatic transmission?



When you encounter the low-power event, do you notice smoke coming from the tailpipe? If yes, what color and how much?



Thanks,



John L.

 

[T Peterson]

Tach stays on zero the entire time of low power. I agree it seems to be heat related, as for the wiring being checked thoroughly, I can only take his word on it, but it just doesn't sound like wiring because it is so predictable (see previous post). As for pins on the ECM, this is the second ECM with the exact same symptoms This one is beyond me. Thanks again for all the brain power going toward my problem. It is a 6 speed 01. I haven't noticed any smoke but I really haven't been looking for it. When I go home today I'll check for it.



Tom

 

[JLandry]

Tach stays on zero the entire time of low power. I agree it seems to be heat related, as for the wiring being checked thoroughly, I can only take his word on it, but it just doesn't sound like wiring because it is so predictable (see previous post). As for pins on the ECM, this is the second ECM with the exact same symptoms This one is beyond me. Thanks again for all the brain power going toward my problem. It is a 6 speed 01. I haven't noticed any smoke but I really haven't been looking for it. When I go home today I'll check for it.

Tom,



When I asked about pins or connectors, I was thinking along the lines of maybe there's a problem with one or more of the "sockets" inside the connector(s) on the ECM or CPS wiring harness not making good contact. It's a long shot to be sure, but has happened.



I'll bet you could nail down where the problem is coming from if you had a Chrysler DRBIII Scan Tool hooked up when the low-power event happened. The DRBIII would show you the sensor inputs and outputs in both the ECM and PCM in real time. You could then see which computer might be missing either a camshaft or a crankshaft position signal. The DRBIII lab scope function could also be used to monitor the CPS output wire to check the signal quality for irregularities.



Assuming there's nothing wrong with the CPS, the ECM, or the wiring harness between the CPS and ECM, I'm wondering if maybe the PCM or it's wiring harness could be faulty? I suggest this because the PCM gets a crankshaft position signal from the ECM over a dedicated line, and what if the PCM stopped reading this information for some reason when it gets hot? I know you'd loose the tachometer signal for sure, and I'm guessing it's possible the PCM could be sending signals back to the ECM (over the CCD bus) telling the ECM to limit power due to a drivetrain problem. One way to rule this out would be to monitor the sensor signals with a DRBIII.



At this point it might help to bring the truck to a good Chrysler dealer who'll hook up a DRBIII and go for a test drive with you to look for causes.



John L.

 

[T Peterson]

I understand now about the socket end of the harness, but don't really suspect wiring because it happens the scenario happens every single cold start. I'd take it to a dealer if I could find a good one, the in town will never see me again. Does it have to be a "Chrysler" scan tool?



Tom

 

[JLandry]

Does it have to be a "Chrysler" scan tool?

From what I know of how code scanners work... you would indeed need the Chrysler DRBIII tool for this level of diagnostic work. A simple code scanner can only pick up data present on the OBDII data bus, and that wouldn't include the camshaft and crankshaft sensor inputs and outputs you're looking for. The DRBIII on the other hand is capable of reading all communications being sent over the CCD (Chrysler Collision Detection) bus, and it can send out signals over the CCD bus to control the various vehicle computers.



You can buy a used DRBIII on eBay starting at around $2000+.



Best regards,



John L.

 

[T Peterson]

YIKES! Never mind about buying one, I guess I'll have to bite the bullet and try the dealer in Temecula or if anybody knows of a good one close by, the one in Escondido is less than worthless for service. Thanks again, and when I find out what the culprit is I'll let ya'll know.



Tom

 

[JLandry]

YIKES! Never mind about buying one

What??? I thought every 2nd Gen 24v Dodge Cummins owner carries a DRBIII in his truck... along with a spare VP44, an ECM, and a PCM! :-laf



John L.

 

[T Peterson]

Pcm Source

I thought I saw a link somewhere in this thread for a PCM source, maybe it was somewhere else but does anyone know of one? I'm taking it to the dealer soon for diagnosis only and want to be prepared when I get the "good" news. Thanks again for all the help.



Tom

 

[JLandry]

I thought I saw a link somewhere in this thread for a PCM source, maybe it was somewhere else but does anyone know of one? I'm taking it to the dealer soon for diagnosis only and want to be prepared when I get the "good" news. Thanks again for all the help.

Tom,



The company is Auto Computer Exchange in Florida. Great folks to work with.



They sell a Dodge Ram PCM for $299 plus shipping charges. No core or exchange is needed. They also sell through eBay.



They'll need to know your truck's VIN and current mileage to program the PCM before shipping it out (or this can be done by anyone with a Chrysler DRBIII diagnostic tool).



Good luck,



John L.

 

[T Peterson]

Thanks again John, you've helped me so much.



Tom

 

[BarryG]

I am in the process of buying an ecm from auto computer exchange as we speak. Did some research on them they seem to be good to deal with. However the ecm they sent me the other day threw more codes than my existing bad one, it also was fairly dirty ie the plug connector had oily dirt on it so it hadnt seen a plug in some time. Didnt exactly give me the warm fuzzies but when I called them they said they would send another one right out. Waiting for it to get here hopefully the second works better. They were helpful and are doing/did what they can will see what happens.



Also as far as the drbIII tool, I'll have to admit I dont have one laying around as I should for just such occassions :-laf but have recently seen several threads here and another site or two where you can rent them. Even renting them doesnt appear to be cheap but significantly cheaper than buying one.

 

[T Peterson]

Let us know how that works out for you. I keep waffling on whether or not to take to the dealer. By the time I rent a car and paying god knows how much for the diagnosis it will probably be just as much as an ECM. I know it could be a bad ground or connection of some sort. Tonight, I'll check the connections and everything else I can with the instructions John sent me and maybe just bite the bullet and go for it if I can't find anything else wrong, either way I'll post the good and the bad.



Tom

 

[JLandry]

However the ecm they sent me the other day threw more codes than my existing bad one, it also was fairly dirty ie the plug connector had oily dirt on it so it hadnt seen a plug in some time.

Barry,



It's actually quite normal for the ECM to be loaded with stored trouble codes if it's been reflashed... especially so if it was reflashed on the bench (off the truck) using a PC as Auto Computer Exchange undoubtedly does. The following text is from Dodge service bulletin 18-033-04 regarding reprogramming the ECM:

NOTE: Due to the Cummins controller programming procedure, a DTC may be set in

other modules (PCM, TCM, BCM, MIC, SKIM, etc. ) within the vehicle, if so

equipped. Some DTC’s may cause the MIL to illuminate. Check all modules

using “Module Scan”, record the DTC’s, and erase these DTC’s prior to

returning the vehicle to the customer. Erase any DTC’s in the PCM only after all

other modules have had their DTC’s erased. ​

So assuming there's otherwise nothing wrong with the ECM you receive, just clear the trouble codes after installation and see how it works.



Of course I'd be put off if I'd received a filthy ECM that was supposed to have been "rebuilt. "



Best regards,



John L.

 

[BarryG]

John:

Truck would start but ran poorly. One of the issues was seriously dead pedal and was pretty much undriveable. One of the codes was an apps irrationality which would explain the new dead pedal issue another one was a 606 which is an internal ecm fault or something like that. However will heed your words when hooking it up.



This evening UPS dropped off the new one so they did send one out right away. Hopefully I can get it up to my truck tommorrow. This one looks much better at least on the outside.

 

[JLandry]

One of the codes was an apps irrationality which would explain the new dead pedal issue...

Barry,



The very first thing to do after installing the replacement ECM is the APPS reset procedure. The ECM could have retained the APPS settings from the previous vehicle. Reset procedure: Turn ignition on to run position, slowly depress accelerator to floor, slowly release, then turn ignition off. Next clear all the DTC's. Some DTC's may persist until the truck is driven enough.



Wishing you success!



John L.

 

[T Peterson]

Barry,

I called the folks that sell the reman PCM and they are quoting more than there website advertises, could you PM me and let me know what you paid? Our trucks are same year except for the back brakes.



Thanks, Tom

 

[JLandry]

Barry,

I called the folks that sell the reman PCM and they are quoting more than there website advertises...

Tom,



Check eBay... Auto Computer Exchange sells there too and items they list on eBay should be the same price as their web page. If you order it through eBay, they have to honor the listed price and you have some recourse in the unlikely event they didn't hold up their end of the transaction. Also, pay with a credit card (if you can) for even more leverage should things go wrong.



Good luck,



John L.

 

[BarryG]

Received my next ecm put it in and all seems well so far. Only about 60 miles on it so far but no codes and runs fine. Hopefully this solves my issue. Have to take a nice long roadtrip with trailer in tow this weekend probably find out then if it is really solved or not.