1994 Coupe 6 Spd - Code 62 stalls then code
Thread Starter
Instructor
Joined: Jan 2005
Posts: 236
Likes: 0
From: Hudson FL
1994 Coupe 6 Spd - Code 62 stalls then code
Hi all,
Cleared all codes, battery fully charged.
My 1994 6spd Coupe LT1 starts and runs perfectly, great idle, revs fine, but once she warms up after about 15 minutes - Coolant Temp 201, Oil Temp 205, she dies. Fans are engaging properly.
I check DTC codes after stall and she pulled C12 --- communicating.
Mod 1. ---
Mod 4. ---
Mod 9. H62
Mod A. nothing
Then I start her she cranks fine, starts runs for few seconds and dies.
I check the codes again
C12 ---
Mod 1. ---
Mod 4. 016
Mod 9. H62
Start her again, starts & runs for a few minutes fine - then dies
same codes
Ive check'd for spark, got spark and it even starts, fuel pump engages for 2 seconds when key turned to on.
all connections to ICM, Coil, ECM, plugs look fine.
Service ASR has come on
I just replaced the Opti/WPump less the 5K miles ago and no coolant leaks.
What the heck !! Need advise here.
Could it be the ECM?
Could it be the ABS / ASR?
Cleared all codes, battery fully charged.
My 1994 6spd Coupe LT1 starts and runs perfectly, great idle, revs fine, but once she warms up after about 15 minutes - Coolant Temp 201, Oil Temp 205, she dies. Fans are engaging properly.
I check DTC codes after stall and she pulled C12 --- communicating.
Mod 1. ---
Mod 4. ---
Mod 9. H62
Mod A. nothing
Then I start her she cranks fine, starts runs for few seconds and dies.
I check the codes again
C12 ---
Mod 1. ---
Mod 4. 016
Mod 9. H62
Start her again, starts & runs for a few minutes fine - then dies
same codes
Ive check'd for spark, got spark and it even starts, fuel pump engages for 2 seconds when key turned to on.
all connections to ICM, Coil, ECM, plugs look fine.
Service ASR has come on
I just replaced the Opti/WPump less the 5K miles ago and no coolant leaks.
What the heck !! Need advise here.
Could it be the ECM?
Could it be the ABS / ASR?
Thread Starter
Instructor
Joined: Jan 2005
Posts: 236
Likes: 0
From: Hudson FL
Delco Opti, Purchased from Partsladi, installed professionally with new delco waterpump.
The reason I dont think it is the Opti because when the opti failed last time there was no rhyme or reason to its intermittant failure.
This time the car runs fine right up until she hits normal operating temp then just dies. I let it cool down for about an hour and she'll start right up and run great right up until she reaches normal op temp and die again.
Also this time around she's throwing a code 62 in mod9 and the ASR light comes on too.
When the opti went bad last time it never coded 62 and didnt throw "Service ASR".
The reason I dont think it is the Opti because when the opti failed last time there was no rhyme or reason to its intermittant failure.
This time the car runs fine right up until she hits normal operating temp then just dies. I let it cool down for about an hour and she'll start right up and run great right up until she reaches normal op temp and die again.
Also this time around she's throwing a code 62 in mod9 and the ASR light comes on too.
When the opti went bad last time it never coded 62 and didnt throw "Service ASR".
Thread Starter
Instructor
Joined: Jan 2005
Posts: 236
Likes: 0
From: Hudson FL
I dont really have good quality test equipment.
I did read that if there is a short or ground issue with EBCT module (ABS/ASR) it can cause drivability and no start issues. I also read that the PCM or ECM can cause these issues, as well as the ICM.
So I guess Im gonna have to bring in in to my mechanic (the guy who installed my opti and pump) and let him figure it out.
I did read that if there is a short or ground issue with EBCT module (ABS/ASR) it can cause drivability and no start issues. I also read that the PCM or ECM can cause these issues, as well as the ICM.
So I guess Im gonna have to bring in in to my mechanic (the guy who installed my opti and pump) and let him figure it out.
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Intermediate
Joined: Jul 2009
Posts: 29
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From: Fairbanks Alaska
Since your engine runs fine for the first 15 minutes, I am thinking your problem may be the ICM, which is more prone to heat related failure. If your Opti was going out, I would expect erratic behavior at all times.
If you have a spare ICM laying around, try swapping.
If you have a spare ICM laying around, try swapping.
Thread Starter
Instructor
Joined: Jan 2005
Posts: 236
Likes: 0
From: Hudson FL
Unfortunately I dont.
But I found this on All Data for my car on Mod 9 - code 62
CIRCUIT DESCRIPTION
The tach pulses circuit provides the EBTCM with an indication of engine RPM to help determine ASR control methods and rates when as ASR event takes place.
DTC WILL SET WHEN
There is a short to ground, short to B+ or an open in CKT 121.
ACTION TAKEN
The "SERVICE ASR" indicator will be "ON."
DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
Checks if the instrument panel tachometer works properly. If so, there is likely an open between the common connection point of the I/P tach wiring and the CKT 121 wiring at bulkhead connector C1OO terminal "G1"
Checks for a short to B+ in CKT 121.
Checks for a short to ground in CKT 121.
DIAGNOSTIC AIDS
A short to ground in CKT 121 with the LT1 (VIN P) engine may cause driveability malfunctions. If the ground is on the ignition system side of the tach filter, there may be a no-start or extremely poor driveability condition. However, these symptoms do not apply to the LT5 (VIN J) engine.
But I found this on All Data for my car on Mod 9 - code 62
CIRCUIT DESCRIPTION
The tach pulses circuit provides the EBTCM with an indication of engine RPM to help determine ASR control methods and rates when as ASR event takes place.
DTC WILL SET WHEN
There is a short to ground, short to B+ or an open in CKT 121.
ACTION TAKEN
The "SERVICE ASR" indicator will be "ON."
DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
Checks if the instrument panel tachometer works properly. If so, there is likely an open between the common connection point of the I/P tach wiring and the CKT 121 wiring at bulkhead connector C1OO terminal "G1"
Checks for a short to B+ in CKT 121.
Checks for a short to ground in CKT 121.
DIAGNOSTIC AIDS
A short to ground in CKT 121 with the LT1 (VIN P) engine may cause driveability malfunctions. If the ground is on the ignition system side of the tach filter, there may be a no-start or extremely poor driveability condition. However, these symptoms do not apply to the LT5 (VIN J) engine.
Intermediate
Joined: Jul 2009
Posts: 29
Likes: 0
From: Fairbanks Alaska
I would recommend that you try to isolate or narrow the fault when the car is NOT starting.
< air > < fuel > < spark >
Which of these are missing when the engine won't start. You can pretty much rule out < air > as a problem(not a common problem with C4's). Get a FP gauge hooked up and observe what it does when the engine peters out. Also, check for spark when the engine refuses to turn over...
Right now, it is unknown whether you have a fuel or spark issue.
< air > < fuel > < spark >
Which of these are missing when the engine won't start. You can pretty much rule out < air > as a problem(not a common problem with C4's). Get a FP gauge hooked up and observe what it does when the engine peters out. Also, check for spark when the engine refuses to turn over...
Right now, it is unknown whether you have a fuel or spark issue.
Instructor
Joined: Jun 2006
Posts: 220
Likes: 30
From: Fairfax VA
I know this is an ancient thread but I recently went though this with my 93 LT1. Info FWIW. Engine stalling, hard to restart, Service ASR light on when still running, Module 9 Code 62, then eventual crank but no start. Since my coil and ignition control module were 30 years old I assumed that any shop I would take it to would replace those right off. I got the coil reasonable price off Amazon and Advance Auto had a 15% off special on the ICM. About $150 for both. Normally it's not smart to just throw parts at it but in this case I thought it would be worth the gamble. Replaced both, started right up and I've put about 500 mile on the car since. Now makes sense since the white wire CKT 121 runs to both of those parts.
Get some thermal paste for the heat sink and the back of the ICM, don't leave this off or use dielectric or other grease.
If you replace the coil and ICM, and still no start, then go to to the manual and trace CKT 121 faults to rule out, or repair the wire.
Get some thermal paste for the heat sink and the back of the ICM, don't leave this off or use dielectric or other grease.
If you replace the coil and ICM, and still no start, then go to to the manual and trace CKT 121 faults to rule out, or repair the wire.
