ECM failing?

[Aloicious]

Ok, so I know ECM failures are uncommon, but Im starting to suspect it, so Im just looking for any thoughts from others before i go looking for a reman ecm.

Basically I have a consistent P0155- bank 2 sensor 1 o2 heater circuit malfunction. Always.

Ive replaced the sensor twice, no change, swapped sensors bank to bank, no change (code does not follow sensor, always bank 2 sensor 1), i found one wire that had been pinched between the bell housing when I did the clutch, so i clipped out the damaged section and resoldered/sealed it up, no change. I went ahead and unwrapped the harness back a ways and clipped out the whole B2S1 connector and soldered/sealed in a whole new pigtail, no change.

Here's the weird part, through all this I can watch live data and the B2S1 and voltage and trims look normal. But whenever the P0155 freeze frame data is reviewed, there is ALWAYS a very strange erroneous value, sometimes its a STFT reading of -38, sometimes its an RPM value of 16,000+. These are never seen in live data, only the code freeze frame data, and obviously outside the capability of the sensor/engine, which is why I'm starting to suspect the ECM.

I know some various jeep models had problems with ecm pins failing internally.

Any thoughts would be appreciated, im kind of at a loss at this point. I don't know what else besides the ECM could be causing this.

This is a 05 sport, 3.7L, 6 speed manual, 4wd, mostly stock libby. 265k miles

 

[Billwill]

All I can suggest is to physically measure all the voltages at the failing sensor and all grounds involved with a Multi-meter and compare it to what you would expect from the Wiring diagram and from what the 2005 Service Manual tells you what to do about this code. Trouble is that this is when the Jeep is stationary and not bumping over roads etc.

It is possible that the wiring getting clamped to the engine may have blown the PCM in that area. The fact that you have replaced the sensor and its wiring would seem to point to the PCM or its pins being faulty...a Breaker yard PCM would have to be re-programmed with the VIN, SKIM code etc.

Cutting out a section of the wiring to the B2S1 sensor may not be good enough...you may need to physically cut off the ends of that circuit...including any splices...and replace them with new wires.

If you have already replaced the B2S1 cabling you could do the same with the B1S1 cabling and swap the two leads over at the PCM by cutting and splicing. The PCM should think that the sensors are still in the same place although they have physically moved....should work I think though I am not an expert on the V6 KJ at all!

 

[Aloicious]

Thanks, yeah ive got to find the ecm pinout diagram to test continuity, the only part that got pinched was right by the B2S1 connector, which is why i replaced the pigtail. The odd freeze frame readings are really what's throwing me off.

 

[Billwill]

You can download the 2005 Jeep KJ Service Manual here...section 8W gives you the wiring diagrams and there are Theory of Operations sections that explain how things work. The wiring diagrams have a pinout section that gives you the pin layout of the PCM and other components. The main thing is to check the wiring colors on all the leads...either solid colors or a color with a thin stripe in another color running though it which is explained in the front of the wiring diagrams.

I had about 9 wiring failures on my 2002 Export CRD after front end collision damaged the large wire harness up front. Although the distance between your PCM and your O2 sensors are about 2 feet point-to-point the these leads usually actually all join up in a large harness that goes all around the engine bay via several connectors. I had the issues that some wires within the harness were fraying through to other random wires and the harness runs through a metal tube in the damaged area...impossible to get to but with a meter I could tell that the damaged wire was showing partial leakage to ground although all motors, solenoids etc. were disconnected ie. finding ground through some other random wire's solenoids etc.

So I had to deal with one failure at a time. I cut off the ends of a failing wire on all ends including splices and replaced the wires with new ones, taking the shortest route point-to point then moved onto the next failing wire.

Having random wires shorting to each other meant that for instance when I turned on my front wipers or the aircon the battery voltage would rapidly rise up to 17 volts at which time the engine would die!

This could be the reason you are getting the weird freeze frame readings..some other circuit is interfering with your O2 wiring!

Jeep KJ Service Manuals: www.colorado4wheel.com/manuals/Jeep/KJ

 

[Aloicious]

Thanks!

 

[Aloicious]

Just to follow up, this was the ECM. I traced and continuity tested as many connections related to this issue as I could and found no issues. Finally I got frustrated with finding nothing I just jumpped into a my suspicion of the ECM, found reman ECM and had it programmed for my libby #'s, and put it in. The codes are gone, runs great, bank 2 goes into CL properly now too (with the P0155 bank 1 would go into CL and bank 2 would stay in OL).

Thanks again for the help Billwil

 

[Bill chase]

My 06 doing something very similar, bad ecm.