No communication with PCM on 2006 TJ 4.0

Superjoe

Superjoe

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California
Hello everyone,

I have a real tricky one here. Seems like a couple of things wrong.

A little back story. This Jeep had a fire behind the radio on the dash. The wiring harness was repaired with solder shrink fit connectors and leads of wire. I plan on replacing this harness in the future once I have a better garage setup. I have a feeling this is causing my fuel gauge not reading correctly and fuel level codes in the computer. I inherited this Jeep with the check engine light on and a bad misfire. I replaced all four O2 sensors with NTK sensors, OEM coil, and NGK spark plugs chasing codes. I also forgot to reinstall the air temp sensor in the intake tube and fried that sensor (sounds like a caused a short also possibly) I replaced the sensor. I had codes P0153 -B2S1 Circuit Slow Response and P2098 -B2 Post Catalyst Fuel Trim Lean after the repairs. I decided it was time to take it to the dealership.

The tech found the vehicle unable to communicate with the DRBIII. He also found a short in the air temp sensor circuit. He is recommending inspectiing the wiring between the OBD II port and the PCM. Does anyone know where/how this is routed behind the dash. It hard to tell if it goes through the firewall on the drivers side or passes across the dash? If the wiring looks good he is recommending replacing the PCM and retesting to see if the vehicle can communicate with the DRB III. Then we can chase circuit short and see why the vehicle is running rough/missing.

Below are all of the notes/codes from my repairs and the dealership visit.

Dealership Tech Notes-

CUSTOMER STATES VEHICLE RUNS ROUGH AND CHECK ENGINE LIGHT IS ON. CONFIRMED LIGHT IS ON. SCANNED VEHICLE WITH DRB III FOUND NO COMMUNICATION WITH DRB III SCAN TOOL. RECOMMEND TIME TO DIAG NO COMM WITH SCAN TOOL. IN GENERIC SCAN MODE, DRB RETRIEVED CODE P0112 INTAKE AIR TEMP CIRCUIT LOW. WITH SENSOR DISCONNECTED DTC FOR INTAKE AIR TEMP HIGH SET. TRIED KNOW GOOD INTAKE AIR TEMP SENSOR PLUGGED IN CIRCUIT LOW CODE RESET. ACTIVE SHORT IN INTAKE AIR TEMP CIRCUIT PRESENT. WITH DRB III NO COMM AND RANDOM CODES THAT RESET, RECOMMEND MORE TIME TO DIAG POSSIBLE ISSUE IN IN HARNESS TO REESTABLISH COMM WITH FACTORY SCAN TOOL AND CONTINUE DRIVEABILITY CONCERNS.


My repairs-

First Scan
P0153 -B2S1 Circuit Slow Response
P3000 -Random Misfire
P2098 -B2 Post Catalyst Fuel Trim Lean

Second scan after drive home
P0153 -B2S1 Circuit Slow Response
P0457- Evap system leak
P2098 -B2 Post Catalyst Fuel Trim Lean
P0463- Fuel Level Sensor Circuit High Input

Replaced Bank 2 Sensor 1 Oxygen sensor and test drove
Light on after 40 miles
P0131 -B1S1 Low Voltage
P0172 - B1 Fuel system Rich


Replaced Bank 1 Sensor 1 and spark plugs
Drove rough but no check engine light for over 100 miles
Check engine light started flashing at idle. Drove 1 mile home and parked.
Scan now shows
P0175 -B1 Fuel System Rich
P0174 -B2 Fuel System Lean
P0151 -B2S1 Low Voltage

Found rubber on spark plug #5 (spark plug socket insulator or material from coil)
Replaced ignition coil
Drove 40 miles light came on
Codes
P2098 -B2 Post Catalyst Fuel Trim Lean
P0463- Fuel Level Sensor Circuit High Input

Replaced both post CAT O2 Sensors
Test drove 30 miles
Light came on codes
P2098 -B2 Post Catalyst Fuel Trim Lean
P0153 -B2S1 Circuit Slow Response

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Wranglerfix said:
I will ask my tech and follow up in a little while. (I would say I’ll circle back to you but that only works if you are press secretary.)
Click to expand...
I bet it it would work in a room.

You guys know why they build round houses.... So cats can't pee in the corner.
 
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@Superjoe Have you gone through the wiring harnesses? The codes you are getting come back to wiring, pcm or both.

is the jeep an automatic or manual? Rubicon or non?

I can test your pcm in my jeep to make sure it’s okay if you would like.

Thanks,

Mark
 
Wranglerfix said:
@Superjoe Have you gone through the wiring harnesses? The codes you are getting come back to wiring, pcm or both.

is the jeep an automatic or manual? Rubicon or non?

I can test your pcm in my jeep to make sure it’s okay if you would like.

Thanks,

Mark
Click to expand...
Hi Mark,

Thank you for your help.
A/T Non Rubicon.
Testing the PCM would be great. That way I could replace or not as necessary.

I have not gone through the harness yet. Only some quick visual inspections. There is some harness repairs behind the center vents. I want to eventually replace this harness to repair the Jeep the correct way. Garage space is not available at the moment. Heater core has to be replaced too. Top, cage, and dash are going to need to come out.

I guess my big question is where the wires from the OBDII port run through the vehicle to get to the PCM.
 
@Wranglerfix I was finally able to test some wiring this weekend. This jeep is a weird one. I found no breaks in the five wires that run from the OBD2 port and the PCM. I did find two wires in different pin locations on the OBD2 port. I’m not sure what to make of this? I guess I should try and confirm my port is PIN out different than others? I used the factory service manual as a guide. Below are the PIN diagrams and a picture of my port. Best case I relocate pins to correct location and have someone hook scanner up to the Jeep.

OBD2 Port

Actual Location ——- Circuit Function —— Service Manual Listed Location
#6 ————- ——- SCI Receive (PCM) ——————- #12
#14 ——————- SCI Receive (TCM) ——————— #15

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9B336E5B-687F-4AB1-B267-497440971088.jpeg
 
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You say you found no breaks. Did you do this visually or a continuity check with a meter? Also, if you did it with a meter, did you also check each wire for a short to ground, or a short to any other wire in the connector (short to power, stray voltage)?
 
ItchyDong said:
You say you found no breaks. Did you do this visually or a continuity check with a meter? Also, if you did it with a meter, did you also check each wire for a short to ground, or a short to any other wire in the connector (short to power, stray voltage)?
Click to expand...
A ome meter won’t tell you shit. Even if it only has one strand of wire connected it can read 0. This sucks to say, I don’t work on cars. I work on construction equipment. When I get a bunch of dumb shit issues I typically try and run a separate wire in parallel to what is messed up. If that doesn’t work most of the time we just replace the entire harness. Only problem with a tj is the harness may be impossible to find and expensive if you locate one.
 
ErikOffroad said:
A ome meter won’t tell you shit. Even if it only has one strand of wire connected it can read 0. This sucks to say, I don’t work on cars. I work on construction equipment. When I get a bunch of dumb shit issues I typically try and run a separate wire in parallel to what is messed up. If that doesn’t work most of the time we just replace the entire harness. Only problem with a tj is the harness may be impossible to find and expensive if you locate one.
Click to expand...
That’s why you check power and your ground with a loaded circuit by back probing a connector or using a test light or headlight with jumpers attached. It’s true that you might need to know what your doing, or at minimum admit that you might not know what you’re doing, before you go and dismiss a tool’s usefulness. 😉
 
ItchyDong said:
That’s why you check power and your ground with a loaded circuit by back probing a connector or using a test light or headlight with jumpers attached. It’s true that you might need to know what your doing, or at minimum admit that you might not know what you’re doing, before you go and dismiss a tool’s usefulness. 😉
Click to expand...
I was talking about trying to find brakes in a wire using omes. Not dismissing the usefulness of the entire tool.
 
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Wranglerfix said:
@Superjoe This goes a little above my ability to answer. My tech will read and respond this afternoon.
Click to expand...
Thank you guys for the info. I understand the the circuit can be tested better. This still doesn’t address the pin locations on my OBD2 port. If the pins are not in the correct location it would make sense why the scan tool can not fully communicate with the PCM. I agree damaged wiring can also cause this. I will look into testing the wires with some voltage behind them. I’m trying to get this thing running and then I’ll look at finding a new harness once I have a better garage setup. The dash harness definitely needs to be replaced as it was repaired.
 
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(Attached a simplified wire diagram from Mitchell 1) You've definitely got something fruity with your OBD2 Port. Someone's done something weird. Pay attention to wire color, de-pin and re-pin the connector and try again.

SCI/PCI = Pins (2,7,9,12,15)
Battery Power = Pin 16
Ground = Pins (4,5)
 

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ItchyDong said:
Real quick, yours is a 2006 4.0L A/T?
Click to expand...
Yes. Originally it was a M/T. Previous owner swapped in the A/T. All original factory parts.
The wire repairs are behind the radio. Fire was in the center of dash. I will get some better pictures of the wiring repairs today.
 
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