Po336
Thread Starter
Joined: Nov 2007
Posts: 841
Likes: 9
From: Holden, MO (KC)
Po336 I finished my new build and went to start the car. It runs but has very rough idle and pops and backfires if you rev it or try and maintain 2-3000 rpm. It's setting a code po336 "crankshaft position sensor circuit range performance". First thing I checked was to make sure all the plug wires were going to the correct cylinders. After doing some searching I've determined it's one of two things. Either a bad CPS or an issue with the wiring or harness for the CPS. Everything is clean and the wires look fine. The second and more likley is the opti has an issue with the low resolution pulse causing the CPS to be out of the acceptable range causing the code. I bought a NIB used MSD opti and just to be safe I sent it to MSD to be checked and ensure it was within factory specs before I installed it. I've learned there are a few others who have used the MSD opti and it pulled a ton of timing causing all sorts of issues and similar symptoms as mine. I got a new scan tool that I'm still trying to learn how to use but it looks like at idle the car has -30 to -38 degrees of timing! My questions are:
-How do I test the harness for the CPS and what is acceptable?
-Is there a way to check the low resolution signal from the opti before I pull it off and send it back to MSD?
It looks like others have solved this by having their tuner modify the timing around the MSD, I've got a PCM4less tune making this pretty much impossible. Thanks for any help you guys can provide.
-How do I test the harness for the CPS and what is acceptable?
-Is there a way to check the low resolution signal from the opti before I pull it off and send it back to MSD?
It looks like others have solved this by having their tuner modify the timing around the MSD, I've got a PCM4less tune making this pretty much impossible. Thanks for any help you guys can provide.
Last edited by 96LT1355Z28; May 25, 2010 at 12:14 PM.
Thread Starter
Joined: Nov 2007
Posts: 841
Likes: 9
From: Holden, MO (KC)
Well the sensor has 11.05 volts at the harness, the battery is low from sitting it has 11.75 volts at the terminals. I called PCM4less and he said he has seen this problem many times with the MSD and Accell opti's. He said the only solution he knows of is to get a GM opti. I called MSD who of coarse denies the issue is opti related and insisted if the PCM set a CPS code then that's where the problem is. So now I'm torn, spend more $ on a GM unit and take my chances spinning it to 68-6900 rpm and having a $500.00 paperweight. Or try and get a local tuner to look at it which will likely involve making changes to the tune wasting the $ spent on the mail order tune! DAMN
PS Still very open to any suggestions!
PS Still very open to any suggestions!
It's your opti. The CPS sensor is just a misfire watch dog. It has no affect on performance. If your sensor or sensor wiring was bad, it would throw the same code, but the car would run just fine.
Thread Starter
Joined: Nov 2007
Posts: 841
Likes: 9
From: Holden, MO (KC)
That's what I'm thinking. Now I just got to figure out if it can be fixed by a tuner or if I'm in the market for another friggin distributor and stuck with a $500.00 billet paper weight.
I doubt it's tune related. I would try to find a GM opti and swap it on and see what changes. I would also thread lock the rotor screws before you install it.
