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VetteVet · 03-26-2011

Darryl,

You may want to check your crankshaft position sensor and it's circuits.

The ECM looks at cam sensor(CMP) pulses and compares them to crankshaft sensor(CKP) pulses. A problem with a crankshaft sensor or crankshaft sensor circuit can set a code 31. I've seen this problem with a GM 8.1L engine. Installed a Mercruiser reman long block. Engine would idle normally with only a very slight burble but would set a cam sensor code shortly after startup. Turned out that it was a damaged reluctor wheel on the crankshaft. I'm not saying that you have a bad crankshaft, just pointing out that when the CKP to CMP relationship check is done by the ECM, a problem on either the CKP or CMP side will set a CMP code.

I hope all of that makes sense.

Jep

03-26-2011	#4
VetteVet Join Date: Jan 2009 Location: Mandeville, LA Posts: 340	Re: CODE 31 Cam Sensor circuit fault.. Help Darryl, You may want to check your crankshaft position sensor and it's circuits. The ECM looks at cam sensor(CMP) pulses and compares them to crankshaft sensor(CKP) pulses. A problem with a crankshaft sensor or crankshaft sensor circuit can set a code 31. I've seen this problem with a GM 8.1L engine. Installed a Mercruiser reman long block. Engine would idle normally with only a very slight burble but would set a cam sensor code shortly after startup. Turned out that it was a damaged reluctor wheel on the crankshaft. I'm not saying that you have a bad crankshaft, just pointing out that when the CKP to CMP relationship check is done by the ECM, a problem on either the CKP or CMP side will set a CMP code. I hope all of that makes sense. Jep