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Hummer H3For the Hummer driver who wants the rugged look and off road capabilities of the Hummer, but in a smaller size and with a more fuel economy friendly engine.
Fingers are crossed that its really fixed this time so we plan to start back on the return camping trip tomorrow.
Well, that didn’t last long. Performance issue returned today crossing through Eastern Washington State and into Idaho. This followed a mostly uneventful full day of driving yesterday through the mountains of British Columbia and a drive through the very hot Okanogan Valley of BC and WA. At the very end of the day yesterday as we climbed into higher terrain in Eastern Washington we started to see it pulling advance again, and this morning on first engine start the check engine and P0328 tripped. I cleared the code and we drove for about three hours, but the code set again to pending then fully set about an hour later. Proceeding past Spokane the advance issue and reports of knock retard became more or less steady (but the engine is not knocking) so we ended up back tracking to visit a dealer service shop rather than head into the higher hills of central Oregon where I need al the performance I can get. The dealer thinks, based on everything we’ve already done, that maybe the knock sensor connector and pigtail has a problem so they will change that for us in the morning …. but I’m not really feeling confident that that is going to be the end of it.
The code is flagging an electrical short to ground or voltage on the knock sensor circuit, but what I don’t know is if the driving performance issues we are seeing (i.e. computer commanded reduced ignition advance/power) is the expected response to that type of fault, or if that could somehow be due to some unrelated undiagnosed issue.
Yes, lol! Skip the dealer...
Contact ivan at pine hollow auto diag. You can find him on you tube. He's located in Pennsylvanian, i believe. Great content and really knowledgeable.
Or south main auto. Or watch wes work. Or wrenching with kenny.
odd they did not replace it when they replaced the sensor. i think there was a tsb out that mentioned replacing both the knock sensor harnes and knock sensor when replacing sensors.
@Doc Olds First mechanic, an independent, said they traced the wiring and checked for high/low shorts per the service information, and also did a careful inspection of the connector for any signs of past shorting, and all checked out ok. I didn’t actually watch them do the work so have to take their word for it. Part of the problem, of course, is the issue only seems to appears when the car is good and hot which makes the troubleshooting more difficult. Driving it to the dealer this morning when it’s still cold and everything is working just fine - no knock retard or reduced ignition advance, no codes, no pending codes.
@bronxteck Thank you - I had not heard about a TSB to do the sensor and connector at the same time, but we’ll swap out that connector this morning. Dealer didn’t stock the part but NAPA got one in overnight for us. I was the first person to change the sensor so if there is a TSB that’s on me. The grey-beard experienced tech at the dealer known as the ‘electrical problem guru’ thinks 99% the issue is in the connector. Hope he’s right! We still have a long drive ahead of us back to NM.
Does anyone know if the PCM will do any sort of reduced ignition advance schedule when the P0328 code is pending? Maybe that’s what we are seeing when the advance is negative 10 but no knock retard is being reported?
I do not think the code itself causes spark retard, but...... a lack of feedback from the knock sensor (out of expected bounds) can cause the negative spark as a default protection against damage.
Final update, I hope. Dealer replaced the knock sensor connector and in the process traced the wire upstream and found a spot about 9 inches up in the main harness where the wire had been chafing against the block and was shorting. The harness loom in that area was brittle from heat and had started to disintegrate, allowing the wire to contact the block.
Two days of driving through mountain passes and through 105 deg weather since the repair and I have not had any ignition advance or knock retard issues. The engine has been toasty warm these past two days - I’ve seen as high as 238 reaching the top of some of the passes, but generally in the 220-235 range with outside temps of 95-105 and elevation from 3000-7000 ft.
Tomorrow we’ll be going through some passes as high as 11000 ft, but temperatures should be in the 80’s so I think we’ll be ok. I sure am glad I installed the scan gauge so I can monitor coolant and tranny fluid temps and intervene to keep them from going open loop.
Added bonus, I’ve seen about a 10% improvement in fuel economy in the 950 miles we’ve driven since the dealer fixed it. 🙂
Final update, I hope. Dealer replaced the knock sensor connector and in the process traced the wire upstream and found a spot about 9 inches up in the main harness where the wire had been chafing against the block and was shorting. The harness loom in that area was brittle from heat and had started to disintegrate, allowing the wire to contact the block.
Two days of driving through mountain passes and through 105 deg weather since the repair and I have not had any ignition advance or knock retard issues. The engine has been toasty warm these past two days - I’ve seen as high as 238 reaching the top of some of the passes, but generally in the 220-235 range with outside temps of 95-105 and elevation from 3000-7000 ft.
Tomorrow we’ll be going through some passes as high as 11000 ft, but temperatures should be in the 80’s so I think we’ll be ok. I sure am glad I installed the scan gauge so I can monitor coolant and tranny fluid temps and intervene to keep them from going open loop.
Added bonus, I’ve seen about a 10% improvement in fuel economy in the 950 miles we’ve driven since the dealer fixed it. 🙂
Thank you for this ^^^ Its good to keep a eye open for any wires laying on the block...
