SES code 372 what is it???
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Joined: Nov 1998
Posts: 71,094
From: Hell was full so they sent me to NJ
Your question has been answered by Rob/Shoebox... you need to read the posts carefully.
The Opti has a cam position sensor that uses an optical sensor and a rotating disc to measure where the camshaft is. There are two different signals that come out of the optical module in the Opti. One is 360 pulses per cam revolution (2 crank revs) and that is called the "high resolution pulse". That pulse is used to meaure RPM and to allow very precise ignition timing.
According to the code, your PCM is not seeing that pulse from the Opti. It is seeing the second pulse pattern that comes out of the Opti... the low resolution pulse, and that pulse pattern is encoded to tell the PCM which cylinder is about to fire, so it can fire the correct injector in sequence.
If the high resolution pulse is missing, the PCM uses the low resolution pulse pattern to set the ignition timing. It is not as accurate, and may cause spark scatter. For all I know, there may be some sort of default corrections made to the timing by the PCM under these conditions.
If you are missing the high resolution pulse, it may explain why the tach is not working, since that pulse is the primary info for the RPM.
Problem is, you have no idea whether the code was caused earlier and is just "stored", or whether it is an "active" code and the pulse pattern is gone. Pulling the SES light is NEVER the way to solve a problem. You lose the benefits of what is really a very powerful diagnostic system in the PCM.
IF the optical pulse is missing, the optical module in the Opti MAY be faulty. If it is, you need to replace, as a minimum the back 1/2 of the Opti. The optical section is the back 1/2, the high voltage (cap/rotor) is the front 1/2. You can buy only the back 1/2 from a parts house. But replacing only part of the Opti is generally not a smart move, unless the other 1/2 has already been done recently. The whole d@mn genuine GM Opti is $190.... if the Opti is bad, just replace it.
But it may be the wires to the Opti. Check the harness connector to the Opti. Make sure the pins are not bent or corroded. Check the Opti harness diagnostic connector, gray connector on the black bracket on the middle of the passenger side of the intake manifod. If the harness is fine, it sounds like the Opti... ASSUMING the code is "active".
The Opti has a cam position sensor that uses an optical sensor and a rotating disc to measure where the camshaft is. There are two different signals that come out of the optical module in the Opti. One is 360 pulses per cam revolution (2 crank revs) and that is called the "high resolution pulse". That pulse is used to meaure RPM and to allow very precise ignition timing.
According to the code, your PCM is not seeing that pulse from the Opti. It is seeing the second pulse pattern that comes out of the Opti... the low resolution pulse, and that pulse pattern is encoded to tell the PCM which cylinder is about to fire, so it can fire the correct injector in sequence.
If the high resolution pulse is missing, the PCM uses the low resolution pulse pattern to set the ignition timing. It is not as accurate, and may cause spark scatter. For all I know, there may be some sort of default corrections made to the timing by the PCM under these conditions.
If you are missing the high resolution pulse, it may explain why the tach is not working, since that pulse is the primary info for the RPM.
Problem is, you have no idea whether the code was caused earlier and is just "stored", or whether it is an "active" code and the pulse pattern is gone. Pulling the SES light is NEVER the way to solve a problem. You lose the benefits of what is really a very powerful diagnostic system in the PCM.
IF the optical pulse is missing, the optical module in the Opti MAY be faulty. If it is, you need to replace, as a minimum the back 1/2 of the Opti. The optical section is the back 1/2, the high voltage (cap/rotor) is the front 1/2. You can buy only the back 1/2 from a parts house. But replacing only part of the Opti is generally not a smart move, unless the other 1/2 has already been done recently. The whole d@mn genuine GM Opti is $190.... if the Opti is bad, just replace it.
But it may be the wires to the Opti. Check the harness connector to the Opti. Make sure the pins are not bent or corroded. Check the Opti harness diagnostic connector, gray connector on the black bracket on the middle of the passenger side of the intake manifod. If the harness is fine, it sounds like the Opti... ASSUMING the code is "active".
Last edited by Injuneer; Jul 26, 2003 at 01:40 PM.
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Joined: Jul 2003
Posts: 553
From: LUBBOCK Tx and Dallas on occasions
yes the code is active would spraying the connections with cleaner help at all? I have a timing cover oilleak and it gets oil on sensors down there thanks for the help
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Jun 23, 2015 07:19 PM