P0501 code but everything works.

[Deth1973]

I'm having an issue with my truck. Its a 2001 dodge cummins 4x4 automatic transmission 4 wheel abs. Im getting the p0501 code with check engine light, and a slight hesitation when the code activates at 20mph. My speedo is working fine and no other lamps on other than the check engine lamp. The code seems to only be in the ECM and not in any other modules. I started going thru mopar1973man's post about this code and at step 2 its saying replace the ABS module. I dont believe this is an ABS module issue because my speedo is working normally. I recently bought this truck knowing it needed a PCM so i ordered 1 and that seemed to have solved all my previous issues(CCD/no bus). The p0501 is the only code it has and like i said it seems to be setting this code only in the ECM. I connected an oscilloscope to both speed sensors and they appear to be operating properly. When i view data on my bosch scanner it shows 2 speed readings. 1 of them reads normal while driving and the other stays at 0. The 1 that stays at 0 i believe is being read from the ECM. Today i connected a snapon modis edge to it to check things out. I checked the speed reading in the ABS module and they appear fine, i also did the same for the PCM and they look good too. The ECM did not have anything that related to vehicle speed. I think i have an ECM issues im just not sure, and nor do i know how i can test that theory. Any help would be greatly appreciated. Does anyone know where to start looking if i were to open up the ECM and start testing components? 

[Haggar]

Interesting.   I looked it up in the 2001 FSM.  P0501 is not on the listed potential fault codes....   P0500 is on the list which is no vehicle speed detected.  (so is that a FSM problem, or do you have a different PCM...  interesting.)

 

But for certain, don't spend time looking at the the ECM for this issue.  The ECM cares not what the vehicle speed is.  (I pasted the ECM inputs and outputs) Only the PCM and ABS care. 

 

Also with an automatic the PCM is resolving 2 "vehicle speed sensors"....    One is the "output shaft speed sensor" and one is the "vehicle speed sensor"   The Vehicle speed sensor is a tone ring on the final drive ring gear.  It is usually used more for ABS and Speed display on the cluster.   The output shaft speed sensor is located on the transmission somewhere.   I assume that is the one you are having trouble with, since you still have speed display.  Good luck.  Hag

 

 

 

 

 

[Deth1973]

Ya, all the pinouts I've found don't show anything about a speed signal. They also show nothing on pin 43, however the speed signal from the ABS is on pin 43. I just picked up a used ECM today that I'm going to try when i get home.

[Haggar]

I found it in the ABS controller wiring too.  It is not a speed signal.  It is a brake sense.  The ecm must want to know if you have the brake depressed.

 

Looking at the section of the manual that refers to the ECM connections,  pin 43 is never mentioned.  See pages 8w-30-29 to 8w-30-42.      on page 8w-30-37  a signal for brake sense comes in on pin 24.  I never saw a wire labled going into the ECM on pin 43. 

 

I agree on 8w-80-40 the connector pin out for the ECM shows pin 43 as a  vehicle speed signal, but none of the other wiring schematics show this at all.  I think the connector pin out is incorrect on labeling pin 43.  and since there is no wiring associated with it, I think it is empty or unused.  I will try to look at mine soon.  I need to pull the fuel manager and look for an oil leak.

 

GL

Hag

[Deth1973]

I replaced the ECM with a used one and it solved the issue. There is a white/orange wire in pin 43 for VSS. It is C2 pin 27 on the PCM and C1 pin 12 on the ABS. Ill have to look into pin 24 and test the old ECM vs replacement ECM to see if there is power or ground on that pin in the old ECM. It might be shorted internally thinking the brake is pressed. It could also be possible that it doesnt want to see the VSS on pin 43 but has the wrong software in it. It is a reman ECM. I also contacted the reman company and it sounds like they might warranty it, just have to send it to them.