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Unread 02-11-2013, 10:02 PM   #1
Registered User
1999 XJ Cherokee 
Join Date: Feb 2013
Location: Dallas, TX
Posts: 2
99 XJ 4.0L Code: P0505

Hello All,

I have a 99 Jeep Cherokee Sport 4.0L 4x4 with 185k miles. The Jeep is running well however I tried to get it inspected and it did not pass because the check engine light (CEL) was on with the P0505 code (IAC [Idle Air Control] system). The inspection person told me that my CEL was probably burnt out which is why I was unaware.

Side note: I found the CEL and airbag lights were actually missing so I replaced them and I purchased a bluetooth OBDII reader from amazon.

The jeep seems to idle well around 750 RPM. If I turn on/off the lights, AC or other accessories the RPM might drop slightly for a second then return to normal. It never feels like it is going to die and the RPMs never spike, it seems pretty consistent around 750RPM.

I replaced the Idle Air Valve and had O'Reilies clear the code and the CEL stayed off on the drive home however after parking and starting the Jeep the CEL has returned.

I attempted the voodoo in this thread: http://www.jeepforum.com/forum/f11/v.../#post12381258 however the code never went away and there were no noticeable changes.

I have figured out how to clear the code with my Amazon-Blutooth-ODBII thing and after some testing I have found the following:

1. Clearing the code with the Jeep on, not started, the CEL light will stay off (either sitting with the jeep just on, or as I drive around).
2. After clearing the code and running the jeep, if I turn the Jeep off then back on (not started) the CEL is back on and the P0505 code is logged.
3. I cannot clear the code when the Jeep is running.

The error seems to happen before the Jeep ever starts, or the code does not get logged until the jeep is turned off.

I got out the multimeter and tested the connection between C1 at the PCM and the 4 pins for the Idle Control Valve. All 4 pins at the idle control valve have 1.5 ohms at their associated spot on C1. I even tested all 4 pins against every other pin in C1 to make sure it did not short to another pin also.

It seems to me the idle control valve is good, the wiring harness is good, and the only thing left is the PCM...

Please let me know if there is anything you think I have missed or I should check before taking the plunge and buying a new PCM.

I am looking at purchasing a PCM from these guys: http://www.autocomputerexchange.com/...-cherokee.html has anyone bought one of these before? Anyone want to recommend I go with a different vendor (cheaper or better reputation)?

Thanks in advance for any help you can provide.


alogon3 is offline   Reply With Quote
Unread 02-25-2013, 03:37 PM   #2
Registered User
1999 XJ Cherokee 
Join Date: Feb 2013
Location: Dallas, TX
Posts: 2

I went ahead an bought a new PCM from Auto Computer Exchange and it seems to have resolved the issue. I am no longer showing a check engine light and I was able to pass the Texas inspection.

I bought the computer from their E-Bay store: http://stores.ebay.com/AUTO-COMPUTER-EXCHANGE . I paid $169.00 on Feb 18th and received the computer on Feb 22nd. If I mail back the old PCM they will provide a lifetime warranty on the new one.

The install was super simple:

1. Disconnect the battery.
2. Locate the PCM (drivers side front of the engine compartment, next to the air box)
3. Remove the 3 connectors to the PCM (there are clips on the top and bottom of the connectors)
4. Remove the 3 screws attaching the computer to the fender. (8mm socket I think.)
5. Install the new computer in reverse order.

I had to drive it around for about 3 days (and 150mi) before the computer had enough data to be inspected.

Hopefully this information will be helpful for someone else in the future.
alogon3 is offline   Reply With Quote

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