Codes P1698 and P1687, PCM/TCM issues

MYJEEPHATESME

MEMBER
2001 JEEP GRAND CHEROKEE
4.7L
V8
4WD
AUTOMATIC
200,000 MILES

After having the issue my vehicle threw two new codes: P1698 no communication from TCM for more than 10 seconds and code P1687 no PIC/BUS msg received. This happened after vehicle was parked for 45 minutes I cranked it to leave and display started to ding and check gauges light came on. I smelled melting wires so I cut engine off. It would not crank again afterwards. I reset codes and disconnected negative terminal but don’t want to try to crank it and damage it further. The smell was coming from the PCM location even after vehicle was towed home hours later. My question is this, will you come fix my car? If not, what do I do to narrow down what the issue is?

Saturday, February 20th, 2021 AT 7:26 PM

4 Replies

JACOBANDNICKOLAS

MECHANIC
110,071 POSTS

Hi,

We are here to help people get their vehicles fixed. However, we don't provide a mobile service.

If you smelled burning wires, have you checked at the PCM to see if there is evidence of damage?

Let me know what you have found or if you have other questions.

Take care and God Bless,

Joe

Was this

answer

helpful?

Yes

No

Sunday, February 21st, 2021 AT 5:06 PM

MYJEEPHATESME

MEMBER
7 POSTS

I forgot to mention it’s a 2001 JGC Laredo 4.7 4wd. No visual damage that I can tell. I had read online while waiting on the tow truck that there are three sets of pins you can check with a continuity voltage meter to see if the PCM is bad or if the problem is elsewhere but I can’t find the article again. Do you know which pins? Also, I was checking fuses in the box under the hood and the fuses are fine but no power going to the fuse for the solenoid and the O2 sensor fuse (both 15s) there was one more not getting any power I can’t remember which one. The battery was hooked up and the key was in the on position and I used a light tester.

Was this

answer

helpful?

Yes

No

Tuesday, February 23rd, 2021 AT 7:56 AM

JACOBANDNICKOLAS

MECHANIC
110,071 POSTS

Hi,

As far as the wires you mentioned, I'm not sure exactly what you want to be checked. The concern is the smell you described. I would be looking for burnt or melted wiring in the harness.

I am attaching the entire schematic for the engine controls/powertrain management. I had to cut the pics in half to make them readable, but I did overlap them so you can follow. Take a look through them and see if they help. They include the entire pin-out of the PCM.

Let me know if this helps or if you have other questions. Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-wiring

Take care and let me know what is found.

Joe

Images (Click to make bigger)