Odd no-start on high mileage unit

mchan68 · February 11, 2022

Vehicle in question is a 2017 with 180K miles. Came in as a no-start. The following has been checked and verified: fuel sample, cam and crank signal, FRP sensor and associated circuitry, good low fuel pressure. While monitoring PIDs during engine cranking, it will build more than sufficient FRP (when actual compared with desired), engine cranks at more than sufficient engine RPM needed, CMP sensor signal switches accordingly. It seems there is no injector pulse width signal during cranking despite all the other PIDs being well within specs. Tried with FRP unplugged and plugged in, no difference. Already replaced the volume control valve as well, with no change in result. Vehicle will start right away with an "alternative fuel source" (a k a Brake Parts cleaner sprayed into intake) temporarily, thus eliminating any possibility of a base engine concern (eg. valve timing, low compression etc.). It does set a P2291 only after extended cranking, despite FRP climbing up to well within the required parameters (about 5000ish psi). What is left? A faulty PCM? Unfortunately, not a part that can be swapped for testing purposes. Asking on behalf of a good friend.

lmorris · February 11, 2022

Pull the crank sensor and inspect the tone ring on the flywheel. If you already haven't. We had one that would just quit for no reason, turned out the tone ring was rusty and there was a chunk of metal on the sensor.

mchan68 · February 12, 2022

I will pass that information along. Thanks. The crank sensor tone ring IS part of the flexplate if I'm not mistaken, correct?

lmorris · February 18, 2022

On 2/11/2022 at 6:58 PM, mchan68 said:

I will pass that information along. Thanks. The crank sensor tone ring IS part of the flexplate if I'm not mistaken, correct?

You are correct. The outer edge of the flexplate is the tone ring.