Codes P0505 and then P0306

pcrawfordpt

pcrawfordpt

Member
Joined
Feb 15, 2021
Messages
68
Location
Big Bear City, CA.
Looking for some insight for my 1997 TJ, 4.0, Auto. A few weeks ago was doing some difficult trails and coming down off the trail, my CEL comes on. Everything looked fine with gauges, however I noticed as the RPM went up/down the Oil Pressure went up/down. When we pulled in the lot to air up, the engine died and would not restart. Didn't have scan tool, but assumed it was either the Oil Pressure Sending Unit or oil pump. Since pressure was going up/down with RPM, figured it was OPSU. Went to Auto Zone and picked up new OPSU and installed. TJ started up and drove home about 5 miles, but was not running well. Took TJ to Auto Zone and ran scan. Code P0505 for IAC. Purchased and replaced. No Change. Thought maybe Throttle Body/IAC needed to be cleaned, so removed and cleaned. Reinstalled, cleared codes, but P0505 returned. Checked for power at IAC connector and am getting power (3 of 4 pins - I believe this is correct as the IAC is supposed to switch power to pins back and fourth?). Thought maybe it needed to Re-Learn? Read that driving for 4 miles at 40 MPH+ does this. Went for drive as instructed and cleared codes. Restarted and code P0505 remained clear. Stopped for gas and when restarted, CEL came back on. Got home and ran scan. Now getting both P0505 and P0306! TJ not running good, but don't necessarily hear misfire. Plugs, cap, rotor and wires are about 6-8 years old, but not a daily driver so not many miles. Thinking to replace all that as it probably needs it regardless. Maybe it's the PCM? Anyone ever experience this?
 
Oil pressure increasing as RPM increases and vice versa is normal. As far as everything else goes, I'm not sure. Also just a heads up if you don't have a code reader you can usually switch the keys to on without actually starting the engine 3 times quickly and where the odometer is it will show you your codes.
 
Update: Diagnostic for faulty IAC valve is to have it throw a code when plugged in, but not throw a code after codes cleared and when disconnected. Passed. However, I am only getting 10.4 volts to the IAC connector? Could that be an issue? Also found PCM had come loose and fallen down into battery tie down. Caused rubbing and actually wore a groove into the PCM housing, and rubbed the plastic coating off some of the wires in the Black PCM harness (where IAC wires live). None of the wires seemed broken, but a few strands were frayed. Separated, inspected, and covered with tape. But...maybe that's why I'm only getting 10.4 volts (spec calls for 10.5-12). Anyone know where I can find out which color works correspond to what device? Going to order a new PCM as even if its not the issue, I wouldn't trust it after it being damaged. Anyone know who makes the best after market PCM? Recommended Wrangler Fix by a friend. Flagship 1?

IMG_0825.jpg


IMG_0826.jpg
 
UPDATE: I spliced in new wires, but unfortunately nothing changed...still throwing code P0505. Still getting 10.3 volts at IAC. I think there must have been a short with the exposed wires, causing a malfunction with my PCM.

Wires exposed, frayed and spliced:
Brown/Light Blue - A6, P/N Position Sensor
Light Green/Black - B12, Injector #6 Driver
Pink/Black - B6, Injector #5 Driver

Wires Exposed, but appeared to only have plastic coating rubbed off, and exposed wire was taped:
White/Orange - B27, Vehicle Speed Sensor
Gray/Yellow - B23, Oil Pressure Sensor
White/Dark Blue - B4, Injector #1

Since the PCM's aluminum casing was also damaged (see attached) from rubbing the battery tie down, I think that either that or a short has damaged the PCM? Note the damaged PCM casing has been like that for over a year. Noticed it and re-secured it, however only recently noticed the frayed wires from rubbing the battery and tie down. Check yours!

Any thought before I order a new PCM?

Thank you!
 
Top Bottom
Back