Random Reduced Power, Low Oil Pressure & P0335


Well-Known Member
Woowee. What a little event I had with my '07 4.2 on the way home from the beach yesterday.

Driving on the highway about 60 mph suddenly I felt the engine lose power, followed the Check Gauges light and CEL coming on (could have been more but again, was driving 60 on a highway and was in a curve), a low pressure oil warning shortly after on the text display (gauge was solid at 50 psi) and then within 2 seconds everything was back to normal except that the tach was reading 0. Truck kept driving normally for a few minutes after so I decided to keep going to home (about 6 miles).

Got home. Shut her off, let sit for a minute and restarted the truck and tach was still at zero. Now a CEL was showing so broke out the OBDII reader but realized I hadn't paired it with my new phone yet, so shut her off, brought stuff from car inside and went back out after about 5 minutes. I restarted the car after pairing the OBDII and read a P-0335 code. Uh oh. Shut her down and did some reading. Restarted her again and checked wiring harness at PCM.

Later in day left for grocery shopping and after start-up CEL cleared. No issues starting, no issues with misfires or other odd engine behavior.

Any thoughts? From what I read this could be anything from an ignition harness issue (plausible as I do have a remote starter installed...yes all the connections are soldered), to a loose ground somewhere or it could be the CKP or it's harness or a damaged reductor wheel. The initial randomness of problem with the dash lights makes me think a harness issue but I guess that if the PCM saw a CKP fault it could have caused a cascading set of issues? Curious on peoples thoughts.

FYI: Currently 146k miles. I do have front hubs set on my to-do list that occasionally cause mild vibrations when turning so maybe something got loosened?


a loose ground somewhere or it could be the CKP or it's harness or a damaged reductor wheel.

More than likely wiring or the sensor itself. Error says a sensor circuit malfunction, not a timing issue so not likely the reluctor wheel itself.

BTW, oil pressure sensor is fake.
Trailblazer oil pressure gauge doesn't tell you the oil pressure (4.2L engines) (YouTube)

If you get a low oil pressure warning, it's likely you had a very low idle speed or stalled engine or the oil pressure switch is defective.


Well-Known Member
You're ruining my day. lol.

So GM decided to use a gauge with a number read out because they felt the sheeple would respond better to an actual number readout instead of a just a light when things go bad. Got it.

Guess I'll be hunting for some wiring issues tomorrow.

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