What do you make of this problem??

[Signe]

My check engine light’s been on for a good year. A month after it came on, I took my KJ to Auto Zone for a quick check. I don’t recall the error code but I think it had something to do with a relay for the AC. Since the AC was working fine, I blew it off. A couple months later I drove by another parts store and had them check it out as well. They told me the same thing.

10 months later I make a 1,200 mile trip pulling a trailer. My KJ ran strong and the AC worked just fine the whole trip. The check engine light was still on. A couple weeks later the AC stopped blowing cold air for a couple minutes and I remember thinking it probably had something to do with that relay. The AC blew nothing but cold air for the next month and then, for a couple minutes one day, it stopped blowing cold air again. It started blowing cold air again after a couple minutes.

A month later I took my KJ to the dealership. The error code they gave me was P0601. The service guy types the code into his computer and tells me I need a new ECU. This really turned me off because he never asked me how long the check engine light had been on nor if my KJ was giving me trouble. Not only that, he immediately called the parts department and said he’s gonna give me an estimate. He’s yet to ask me a single question and he’s yet to take my KJ out for a spin. I politely told him not to bother with the estimate.

I drove down the street to another Auto Zone and they give me the same error code: P0601. The printout he gives me says the probable causes are:

1) A shorted input sensor
2) A shorted electrical circuit
3) Failed ECM

He asks me how my KJ is running and I tell him it’s running as strong as ever (it’s got almost 93,000 miles.) He then tells me it’s unlikely the ECU is bad because, at the least, my KJ wouldn’t be running well. I never told him about the AC because, as I type this, it’s been blowing nothing but cold air.

P.S. The same printout I got from Auto Zone says the definition of P0601 is "ECM internal fault." The explanation reads "ECM unable to communicate on the SPI line."

 

[NineFingerFury]

When I worked at a shop, we'd look up the code and trace signals to the ECM. If the signals going to the ECM are all good, then the ECM is bad. If signals are bad to ECM, check wiring and sensor components and replace/repair what's needed.

 

[tjkj2002]

1st problem is you went that long with the MIL on,2nd is replacing the PCM is the only way to clear that code since it's a fault with the PCM's memory.If you do not fix it you will never know if another issue has come up since the MIL will already be on.


Oh and the AC system will never turn on the MIL in a KJ.

 

[Signe]

When I worked at a shop, we'd look up the code and trace signals to the ECM. If the signals going to the ECM are all good, then the ECM is bad. If signals are bad to ECM, check wiring and sensor components and replace/repair what's needed.

Do you know if a dealership has the capability of running a test that will enable them to pinpoint the exact problem? In other words, can a test tell them if the ECU needs to be replaced or if it's the signals that are bad?

Something I should have mentioned earlier is that back in '09 I took my KJ to the dealership for the 60k service. In addition to replacing the spark plugs, cleaning the fuel injectors, etc., I was told I needed new coils and a new ECU. I paid for the coils. As for the ECU, they told me it wouldn't cost anything to replace it because it was still covered under warranty due to emissions. As far as I know, they did replace the ECU.

As long as we're on the subject of ECU's and warranties, would you happen to know if this second ECU is still under warranty because of emissions-related reasons? On a final note, I used to live in your neck of the woods (I used to live in SeaTac.)

 

[Signe]

1st problem is you went that long with the MIL on,2nd is replacing the PCM is the only way to clear that code since it's a fault with the PCM's memory.If you do not fix it you will never know if another issue has come up since the MIL will already be on.


Oh and the AC system will never turn on the MIL in a KJ.

I agree that I shouldn't have waited so long (but since the initial code was AC-related and the AC was working fine, I didn't think anything of it.)

I really do appreciate your help.

 

[tjkj2002]

The PCM is only covered for 8 years/80k when it was 1st put in service(1st buyer drove it off the lot).Replacement PCM's have a 12 months/12,000 miles warranty if bought(or warrant paid for) and installed at the dealership.

Any dealership can look up your records to see if the PCM was in fact replaced if done at a Chrysler dealership.