Crandall

I am getting code P0372 Timing Reference High Resolution signal A Too Few Pulses, my question is do i need to replace opti, or is there anything else i can check out, also when this issue happend my rpm gauge quite working?

Injuneer

1995 is still OBD-1. That code is OBD-2. Did you swap in a 96/97 PCM? Always a lot of confusion with the combination of the 95’s OBD-1 PCM with the 16-pin OBD-2 style DLC.

The code (DTC 36 in OBD-1) for the missing high resolution pulse does not prevent the engine from running. Its absence does slightly increase spark scatter, which in theory you shouldn’t even notice, but in practice you might. The code could also be caused by a problem with the harness, corroded or damaged connectors. Tach issue isn’t also odd because the PCM derives the RPM from the low resolution pulse.

Are you experiencing any issues with the way the engine starts and runs?

Injuneer

Is this still the same Opti you had this problem with before?

https://www.camaroz28.com/forums/lt1...rms-up-886358/

Crandall

Wow you still remember me!!, no this is a new camaro its a 1997 z28, the signature still is not working right, but yes the car a while to start, runs pretty good, no major misses or anything.

Crandall

Wow you still remember me!!, no this is a new camaro its a 1997 z28, the signature still is not working right, but yes the car a while to start, runs pretty good, no major misses or anything.
Injuneer is who i was saying still remembers me
new car is 1997 30th anniversary camaro z28, cold air intake, borla cut outs, different rear end(i will have to look up what rear end is in it now

Injuneer

I just wondered why the code did not match the vehicle in the signature, so I looked up your old posts and found the one from 2 years ago.

Clear the code and see how fast it comes back. What brand Opti and how old is it? Could be the Opti, the harness, the connector, oil leaking into the Opti due to a bad timing cover Opti seal, etc.. Big problem is it is extremely hard to find a reliable replacement.

Crandall

Hmm i tried to clear the code by just disconnecting the battery, if that would clear it, it comes back immediately. The opti is likley some cheapo, he did do good upkeep on the wires i can see, you cannt really see any of the connections going into the opti, or i might be mistaken, let me know if you have any pointers before i start taking it apart

Injuneer

Some of the newer Optis have a cable permanently attached, so no connector at the Opti.

One good way to check the high res pulse signals from the Opti - at the gray connector on the bracket on the passenger side of the intake manifold, attach a voltmeter to the high res signal wire (purple/white) and the "reference low" (pink/black) wire. Set meter to DC volts, low range. Turn key to "run" (do not start engine). While watching the volt meter, have someone rotate the engine (via the crank hub bolt) very slowly. The volt meter should switch back and forth between 0 volts and 5 volts. The signal will change rapidly, because there are 360 slots, each 1-degree wide on the shutter wheel for the optical sensor.

As noted, if you can live with the slow start, and have no issues with misfires, surging, stumbles, etc., just live with P0372 until the rest of the Opti gives out (P1371 for the low res = engine won't run), or the engine starts to show signs of running poorly. Then check back and see if anyone has updated feedback on the various available Optis. There's been some good feedback on a unit from Petris, but I recently saw a report from someone on ltxtech.com that he had seen negative feedback on Petris on another site. But he can't remember where he saw it. There is also someone who rebuilds the units on ebay that is supposed to be reliable.

Crandall

Very thankful as always for your info, you know these cars better than anyone

Crandall

Very thankful as always for your info, you know these cars better than anyone