Checking for bad ground on 81
Thread Starter
Burning Brakes
Joined: Apr 2011
Posts: 1,017
Likes: 229
From: Bay City Michigan
Checking for bad ground on 81
Trying to find the problem on my 81 that after running for 5 to 10 minutes gives me a CEL. After disconnecting the negative battery cable it clears the ECM but light comes on again after a few minutes of warm up. I have done the test per shop manual to short the two terminals on the ALCL connector but getting a ton of codes, 12, 13, 14, 15, 21, 22, 23, 24, 32 and so on. Also have a OTC Monitor 85 that now gives me the same thing. My Next step is to check for bad ground somewhere, battery cable, ground to engine? What and where should I start to check . Thanks for the help, confused and getting close to ordering new , old Q jet from 80 or before and HEI dizzy.
Racer
Joined: May 2006
Posts: 352
Likes: 42
Trying to find the problem on my 81 that after running for 5 to 10 minutes gives me a CEL. After disconnecting the negative battery cable it clears the ECM but light comes on again after a few minutes of warm up. I have done the test per shop manual to short the two terminals on the ALCL connector but getting a ton of codes, 12, 13, 14, 15, 21, 22, 23, 24, 32 and so on. Also have a OTC Monitor 85 that now gives me the same thing. My Next step is to check for bad ground somewhere, battery cable, ground to engine? What and where should I start to check . Thanks for the help, confused and getting close to ordering new , old Q jet from 80 or before and HEI dizzy.
Code 12 means the list is starting:
Codes List:
code 13 =1 flash followed by 3 flashes =>oxygen sensor
code 14 =1 flash followed by 4 flashes =>coolant sensor
code 15 =1 flash followed by 5 flashes =>coolant sensor
code 21 = 2 flashes followed by 1 flash =>throttle position sensor
code 22 = 2 flashes followed by 2 flashes=> throttle position sensor
code 23 = 2 flashes followed by 3 flashes=> manifold air temp sensor
code 24 = 2 flashes followed by 4 flashes=> vehicle speed sensor
code 25 = 2 flashes followed by 5 flashes=> manifold air temp sensor
code 32 =>egr system
code 33 =>map sensor
code 34 =>maf sensor
code 35 => idle air control
code 41 => cylinder select error
code 42 => electronic spark control
code 43 => electronic spark control
code 44 => lean exhaust
code 45 => rich exhaust
code 51 => PROM
code 52 => fuel calpak
code 53 => system over voltage
code 54 => fuel pump circuit
code 55 => ecm
code 62 => oil temp
Thread Starter
Burning Brakes
Joined: Apr 2011
Posts: 1,017
Likes: 229
From: Bay City Michigan
Pulled negative battery cable for 5 mins then restarted, light was out but came back on again soon. Car idles crappy, like its getting too much fuel, also driving it the shifts are late when hitting the gas. Seems like its confused, must be the lock up converter getting bad signals? I am going online today to find new prices on Q jet and HEI distributor, tired of messing around with it. Assume a 79-80 non computer controlled carb is what I need, was thinking about Edlebrock AVS2 but looks like I would need a adapter plate and then not sure if I can use my stock air cleaner setup?
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
if popping every code there is, either every component works good and then fails at the same time or the ecu is afu. b uy a 80-earlier carb. 80-earlier HEI distributor and toss the whole system.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
If you don't have the stock '81 carb and distributor on the engine now, the computer doesn't have a clue what is going on with it.
As far as "checking for grounds", you just need to identify them, remove/clean/replace them, and verify that they get back to electrical ground at the chassis. Then you can check to see if the system does anything 'different'.
As far as "checking for grounds", you just need to identify them, remove/clean/replace them, and verify that they get back to electrical ground at the chassis. Then you can check to see if the system does anything 'different'.
Thread Starter
Burning Brakes
Joined: Apr 2011
Posts: 1,017
Likes: 229
From: Bay City Michigan
7T1vette, yes, my car has stock carb and distributor , have put 1000 miles on the car with no issues until the mysterious filled the gas tank and then when leaving gas station CEL came on. I have read in my shop manual the CCC is not smart enough to know anything about the gas tank so I guess it was time for it to start behaving badly. I will save the parts for the future owner down the road for sure.
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
My suggestion would be to drive it for about 50 miles (or so) to see if the CEL goes out. As I mentioned earlier, if the ecm is not connected to the entire system (as intended), it will likely throw trouble codes continuously.