No Start, P1694. Tons of work done, not sure where to start

All,
I am in the process of building an 89 Comanche with a full 1998 cherokee swap. Everything from the comanche is gone, so the vehicle is effectively a 98 cherokee for diagnostics. Everything has been swapped over at this point.



I am unsure of where to start my diagnostics and I need some guidance. I am getting no spark and I am receiving several DTC's. Namely P1694 and occasionally P1698 and P0700.


I am worried there is a wiring issue or one of the PCM/TCM modules has failed. The entire wiring harness was removed and installed into the comanche, which is a lot of movement for 25 year old wiring and components..


All the underhood grounds were thoroughly cleaned and in reinstalled today as well. I have the factory FSM, but it doesnt seem to give much guidance for troubleshooting this issue.

A few other things I should add. The CPS is a new Mopar unit. The gauges are not working unless I unplug the airbag controller under the center console. With the battery disconnected, I am reading 60 ohms between OBDII pin 3 and pin 11, which I understand indicates that one of the CCD Bus systems is having an issue?

Make sure all of your grounds have good connections and you haven't missed any.

Code P1694 Jeep

Possible Causes CCD Bus (-) circuit open between Powertrain Control Module (PCM) and Transmission Control Module (TCM)

CCD Bus (+) circuit open between PCM and TCM Transmission

CCD bus wiring damaged

Faulty TCM

I am receiving the following codes:

• P1282 (I have fuel pump relay out while diagnosing this ASD issue) Fuel pump primes as normal when installed
• P0118 coolant temp circuit high
• P1694 No bus from ECM
• P0705 Trans range circuit (reverse lights function, new NSS installed)
• P1698 Fail to communicate TCM (this has come and gone a few times)

The following is my diagnostics so far based on other threads:

• No power at fuse 24 (ox sensor) and 21 (PCM, ignition coil)
• If ASD relay bypassed (30-87 jumped), power at above fuses.
• Battery disconnected, key off. 60 ohms between DLC pin 11 and 3
• Key on bat connected DLC. Pin 3-4= 2.51v, pin 11-4= 2.49v (is this reversed????)
• All underhood grounds thoroughly cleaned, (jeepcables big 7 kit installed as well)
• Infinite resistance on CPS (new mopar unit)
• 5.1v at orange wire on TPS
• No SKIS on this vehicle
• Pin 28 to pin 30 on PCM C3 slot (not on the connector) reading 120ohm

More troubleshooting today:

• TCM ground wire 24 good, 0.0ohms resistance
• PMC ground wires 31 and 32 good, 0.0 ohms resistance
• TCM diagnostics WIRING PASSES ALL FSM TEST (Ohm specs, voltage specs in gears, 2.49/2.51v tests)
• removed gauge cluster and DLC ohms between 4 and 11 jumped up to 120? recall I've been getting 60ohms with everything connected..
• Just to confirm, swapped out another CPS, no change
• Swapped out an extra PCM I have from another 98, though this one is a manual trans. No change, same P1694 code comes up

Just to throw this out there but,... Are you using the engine sensors that matches the new PCM?

The sensors are all the same as were on the engine when it was still (running) in the XJ. The only sensor I replaced preemptively was the CPS with a mopar unit. I did test it with whatever was on there previously (the known-good unit) and that did not make a difference.

Few more things I checked today:


Good checks:

• CCD bus - and + between PCM and TCM both check out good, 0.2ohms.
• Confirmed that 5v remains active to the sensors while cranking
• CkPS output wiring test, PMC C1 BLACK A8 ---> K24 18GY/BK CkPS signal wire CHECKS GOOD

Bad checks:

• Injectors are not firing, in addition to the no spark
  • I did notice with a noid light, that the injectors fire ONCE right as I stop cranking and the engine winds down..
• CPS (distributor phase plate) wiring test, PMC C1 A18 ---> K44 18TN/YL CPS signal wire NO CONNECTION, OPEN LINE
• PCM to coil wire test, PMC C1 A7---> K19 18GY IGNITION COIL NO. 1 DRIVER NO CONNECTION, OPEN LINE

So with this in mind, I am starting to trace the wires from the passenger side of the motor back to the PCM, as it appears there is an issue along the length of those wires. However, this does not explain the P1694 code nor the lack of injectors firing...

Welp.. It appears my firewall cutting had collateral damage. How needlessly foolish of me. Based on the wires cut, it appears to explain all of the engine codes and lack of start. Harness repaired and to-be reinstalled in a few days. At least I learned a lot about the wiring and PCM systems...



(Wires cut include trans range sensor, camshaft signal (distributor phase plate), engine coolant temp signal, ignition ground signal, MAP signal...) Oh brother. Stay humble I suppose.

Yeah, that might the culprit!!

Tedious but an easy fix. Make sure you stagger the splices as best as you can so it's not all bulked up in one spot.