Codes: I need a little help
Thread Starter
Heel & Toe
Joined: Jul 2020
Posts: 21
Likes: 3
Codes: I need a little help
I've got a 1994 Auto, LT1 and have recently gotten the following codes: C12 (which is good, I understand), H32 EGR code and a H48 MAF code. The car runs like it's only running on 5 or 6 cylinders at idle and all mid throttle operation. When the engine is warmed up it needs to be shifted into neutral and accelerator used to keep it running. It also requires a little accelerator pressure to start after being shut down warm. When cold. it jumps to life just fine. FYI, the opti-spark was replaced in 2016 along with plug wires and ECM, and its been running fine until these codes appeared the other day. I'm wondering if disconnecting the electrical connections at the ECM and MAF to ensure the contacts are clean would be a good place to start. Thanks for any assistance you may offer.
Safety Car
Joined: Aug 2002
Posts: 3,842
Likes: 230
From: SANTA CRUZ CA
Safety Car
Joined: Jan 2004
Posts: 4,549
Likes: 343
From: Glastonbury CT
In the open loop it runs fine when first starting NO! When car is warm closed loop runs poor! Try the opti look for water from water pump which mounts over opti if so it is the opti A lot of items to consider do you have history on car? One owner? What has been replaced? Have you looked for simple things like some item loose or disconnected under hood spark plug, vacumn, line dirty air filter which can mud up pintle for air flow. Who was last under hood or under car? How about your 02 sensors are they connected? Do you have the Helmes two part for 94 Corvette manual? If not get it if you are keeping car.
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Thread Starter
Heel & Toe
Joined: Jul 2020
Posts: 21
Likes: 3
Didn't see an evidence of coolant leaking. Not a 1 owner car. No real history except that the opti and ECM were replaced in 2016. I have the bill that came with the car. Nobody has been under the hood or under the car since I got it. I've looked for disconnected/cracked vac lines and have found none so far. Air filter is clean. Haven't checked the O2 sensors but I doubt that they just fall off. The car has been running fine until recently. Don't have the manual mentioned and the jury is still out as to whether or not I plan to keep this car long term.
Team Owner
Joined: Sep 2001
Posts: 62,153
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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Best money you can spend if you want to work on the car yourself is the Helm manual.
Burning Brakes
Joined: May 2002
Posts: 755
Likes: 42
From: Sierra Foothills, State of Jefferson
Or go to Rockauto, look up your car, look in Literature, The should be a Dave Graham CD version of the FSM for $21.00
You may be able to find a used Helm manual in the C$ subsection for parts. I have both, the actual paper manual is a little easier to use when wrenching on the car.
You may be able to find a used Helm manual in the C$ subsection for parts. I have both, the actual paper manual is a little easier to use when wrenching on the car.
Last edited by KurtK; Oct 26, 2020 at 04:42 PM.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Or go to Rockauto, look up your car, look in Literature, The should be a Dave Graham CD version of the FSM for $21.00
You may be able to find a used Helm manual in the C$ subsection for parts. I have both, the actual paper manual is a little easier to use when wrenching on the car.
You may be able to find a used Helm manual in the C$ subsection for parts. I have both, the actual paper manual is a little easier to use when wrenching on the car.
And just to be sure, OP, which module were those codes listed under? The dash lists codes for the CCM first (Module 1), then the PCM (Module 4), then the EBTCM (Module 9). Just listing a code here doesn't guarantee that it's actually the right one, as the same number can mean a completely different thing for a different module. So just to be totally clear, please do list what codes come up under which modules.