Help With retrieving active codes 94 LT1 6spd...
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Joined: Jun 2009
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From: San Diego CA
Help With retrieving active codes 94 LT1 6spd...
Hi guys, Ive been using the search feature but keep coming up empty handed...
Every time I drive my car for more than about 15 min in the city or traffic my check engine light comes on and car runs pretty rough and hesitates, seems to happen about at 230 on the coolant digital gauge.
Once I get home I immediately try to pull the codes but I can never get an Active code... Here is what Im getting:
Module 1: H72
Module 4: H23, H64
Module 9: H62
A:---
I have removed the Negative terminal from the battery also to clear the codes but they still come up.
Any advice on how to figure out what is causing my check engine light to always come on.
Ive already replaced both O2 sensors & MAF sensor. Car ran A LOT better after that but still has the same problem.
I even took off the IAC valve and cleaned it as well as the ignition coil, module, and cooling fins cleaned it out really good and used some washers so it has about a 1/2" spacing from the engine block to reduce heat, that seemed to have the most improvement, and car will run good for a longer period of time before it still reverts back to my same problem.
Oh I have also noticed while the check engine light is on and car is running rough at a stop light, the RPM will drop a bit and all of a sudden its running smooth again, Im assuming thats when the computer is switching back to Closed loop.
I appreciate any help! Thanks!
Every time I drive my car for more than about 15 min in the city or traffic my check engine light comes on and car runs pretty rough and hesitates, seems to happen about at 230 on the coolant digital gauge.
Once I get home I immediately try to pull the codes but I can never get an Active code... Here is what Im getting:
Module 1: H72
Module 4: H23, H64
Module 9: H62
A:---
I have removed the Negative terminal from the battery also to clear the codes but they still come up.
Any advice on how to figure out what is causing my check engine light to always come on.
Ive already replaced both O2 sensors & MAF sensor. Car ran A LOT better after that but still has the same problem.
I even took off the IAC valve and cleaned it as well as the ignition coil, module, and cooling fins cleaned it out really good and used some washers so it has about a 1/2" spacing from the engine block to reduce heat, that seemed to have the most improvement, and car will run good for a longer period of time before it still reverts back to my same problem.
Oh I have also noticed while the check engine light is on and car is running rough at a stop light, the RPM will drop a bit and all of a sudden its running smooth again, Im assuming thats when the computer is switching back to Closed loop.
I appreciate any help! Thanks!
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Your check engine light references the PCM, module 4.
DTC 23 is Air temperature sensor. On right side of air intake, make sure it is plugged in, check for bad pin connections and an open sensor. At approx 85*F, should read about 2238 ohms.
DTC 64 is right front O2 sensor. What brand of O2 sensor are you using? It needs to be Delphi or GM Delco. Any other brands will give possible problems.
Module 9 DTC 62 is Tach pulses malfunction. Just a few suggestions.
The coil feeds the tach filter which then feeds the EBTCM brake computer (behind driver seat). I guess a coil or a tach filter might cause this DTC. A bad connection would do the same thing. I would say the EBTCM could act up also. If the tach works OK that might mean the tach signal is good. But that might not hold true if the amplitude of the signal is low and the EBTCM does not like it.
DTC 23 is Air temperature sensor. On right side of air intake, make sure it is plugged in, check for bad pin connections and an open sensor. At approx 85*F, should read about 2238 ohms.
DTC 64 is right front O2 sensor. What brand of O2 sensor are you using? It needs to be Delphi or GM Delco. Any other brands will give possible problems.
Module 9 DTC 62 is Tach pulses malfunction. Just a few suggestions.
The coil feeds the tach filter which then feeds the EBTCM brake computer (behind driver seat). I guess a coil or a tach filter might cause this DTC. A bad connection would do the same thing. I would say the EBTCM could act up also. If the tach works OK that might mean the tach signal is good. But that might not hold true if the amplitude of the signal is low and the EBTCM does not like it.
Thread Starter
Advanced
Joined: Jun 2009
Posts: 87
Likes: 0
From: San Diego CA
Your check engine light references the PCM, module 4.
DTC 23 is Air temperature sensor. On right side of air intake, make sure it is plugged in, check for bad pin connections and an open sensor. At approx 85*F, should read about 2238 ohms.
DTC 64 is right front O2 sensor. What brand of O2 sensor are you using? It needs to be Delphi or GM Delco. Any other brands will give possible problems.
Module 9 DTC 62 is Tach pulses malfunction. Just a few suggestions.
The coil feeds the tach filter which then feeds the EBTCM brake computer (behind driver seat). I guess a coil or a tach filter might cause this DTC. A bad connection would do the same thing. I would say the EBTCM could act up also. If the tach works OK that might mean the tach signal is good. But that might not hold true if the amplitude of the signal is low and the EBTCM does not like it.
DTC 23 is Air temperature sensor. On right side of air intake, make sure it is plugged in, check for bad pin connections and an open sensor. At approx 85*F, should read about 2238 ohms.
DTC 64 is right front O2 sensor. What brand of O2 sensor are you using? It needs to be Delphi or GM Delco. Any other brands will give possible problems.
Module 9 DTC 62 is Tach pulses malfunction. Just a few suggestions.
The coil feeds the tach filter which then feeds the EBTCM brake computer (behind driver seat). I guess a coil or a tach filter might cause this DTC. A bad connection would do the same thing. I would say the EBTCM could act up also. If the tach works OK that might mean the tach signal is good. But that might not hold true if the amplitude of the signal is low and the EBTCM does not like it.
For the O2 sensors I believe I got Delphis, They were off ebay, made sure they were the 4 wire heated ones.
I havent had any problems with my Tach gauge as far as i have noticed. Would this cause the rough idle at high engine temps though?
Thanks again
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
The causes of these problems are vast. There could be separate root causes causing separate symptoms. There are lots of possibilities here.
Did all this start happening at once, or was it a progression of problems.
I would still check out resistance of the new IAT. Might want to connect the old one to eliminate a bad new part…..if possible.
At the high temperature, how does it run under acceleration. I say this because the roughness can be caused by the opti. A lot of times they act up when they are hot. They may also cause the tach to bounce around some.
I would like to get a scanner on it and look at the swing voltages of the O2 sensors in closed loop. Might give a clue.
Of course roughness can be caused by plugs, wires, coil or ICM at the temperatures you speak of. I would also verify my fuel pressure just to confirm or eliminate that.
I have heard of the ICM being spaced from the head with washers. Even though the head is hot, the purpose of the heat sink grease and flush mounting is to dissipate heat from the ICM to the head. It may run to hot just hung out there not mounted as originally done. I have no definite data on this but just something to consider.
Also just wondering if you feel the cooling system is working OK. When was the last time you changed the coolant or thermostat. Have you checked for debris in front of condenser or between condenser and radiator. What was the outside air temp when you get to 230.
Did all this start happening at once, or was it a progression of problems.
I would still check out resistance of the new IAT. Might want to connect the old one to eliminate a bad new part…..if possible.
At the high temperature, how does it run under acceleration. I say this because the roughness can be caused by the opti. A lot of times they act up when they are hot. They may also cause the tach to bounce around some.
I would like to get a scanner on it and look at the swing voltages of the O2 sensors in closed loop. Might give a clue.
Of course roughness can be caused by plugs, wires, coil or ICM at the temperatures you speak of. I would also verify my fuel pressure just to confirm or eliminate that.
I have heard of the ICM being spaced from the head with washers. Even though the head is hot, the purpose of the heat sink grease and flush mounting is to dissipate heat from the ICM to the head. It may run to hot just hung out there not mounted as originally done. I have no definite data on this but just something to consider.
Also just wondering if you feel the cooling system is working OK. When was the last time you changed the coolant or thermostat. Have you checked for debris in front of condenser or between condenser and radiator. What was the outside air temp when you get to 230.
Thread Starter
Advanced
Joined: Jun 2009
Posts: 87
Likes: 0
From: San Diego CA
The causes of these problems are vast. There could be separate root causes causing separate symptoms. There are lots of possibilities here.
Did all this start happening at once, or was it a progression of problems.
I would still check out resistance of the new IAT. Might want to connect the old one to eliminate a bad new part…..if possible.
At the high temperature, how does it run under acceleration. I say this because the roughness can be caused by the opti. A lot of times they act up when they are hot. They may also cause the tach to bounce around some.
I would like to get a scanner on it and look at the swing voltages of the O2 sensors in closed loop. Might give a clue.
Of course roughness can be caused by plugs, wires, coil or ICM at the temperatures you speak of. I would also verify my fuel pressure just to confirm or eliminate that.
I have heard of the ICM being spaced from the head with washers. Even though the head is hot, the purpose of the heat sink grease and flush mounting is to dissipate heat from the ICM to the head. It may run to hot just hung out there not mounted as originally done. I have no definite data on this but just something to consider.
Also just wondering if you feel the cooling system is working OK. When was the last time you changed the coolant or thermostat. Have you checked for debris in front of condenser or between condenser and radiator. What was the outside air temp when you get to 230.
Did all this start happening at once, or was it a progression of problems.
I would still check out resistance of the new IAT. Might want to connect the old one to eliminate a bad new part…..if possible.
At the high temperature, how does it run under acceleration. I say this because the roughness can be caused by the opti. A lot of times they act up when they are hot. They may also cause the tach to bounce around some.
I would like to get a scanner on it and look at the swing voltages of the O2 sensors in closed loop. Might give a clue.
Of course roughness can be caused by plugs, wires, coil or ICM at the temperatures you speak of. I would also verify my fuel pressure just to confirm or eliminate that.
I have heard of the ICM being spaced from the head with washers. Even though the head is hot, the purpose of the heat sink grease and flush mounting is to dissipate heat from the ICM to the head. It may run to hot just hung out there not mounted as originally done. I have no definite data on this but just something to consider.
Also just wondering if you feel the cooling system is working OK. When was the last time you changed the coolant or thermostat. Have you checked for debris in front of condenser or between condenser and radiator. What was the outside air temp when you get to 230.
Ill swap out the new IAT sensor with the old one to see if the DTC doesnt come back on.
Under high temps at a stop or idling the car shakes/vibrates and the RPM's will go up and down slightly, maybe in the range of less than 100. If I let off the clutch slowly as it engages, the car hesitates, shakes and almost stalls until I give it more than usual gas and it will go, once the car is moving it seems to be fine, Just coming and moving from a stop. Usually the outside air temps are around 72-80, but has done this in the middle of the night when its about 62 also. I do remember one time before I cleaned the ignition coil and fins when it was acting up even on the freeway i couldn't get over 75 without what almost seemed to be it misfiring.
I tuned it up about 1.5 yrs ago, new gm cables, new plugs, new fuel filter & air filter so I don't think that would be my problem, Im really hoping its not the Optispark, I guess the only way to find out is hooking my car up to a computer and scanning it, i just need to get a hold of an ALDL cable...
I also think my cooling system is not running as well as it should be, I know the LT1's were meant to run hot but it always gets up to 230-235 after only a few minutes of driving and that seems to be when my car acts up. I haven't changed the coolant since i've owned the car and I believe the Thermostat is the original, I've looked under and in between the condenser and radiator and it was clean, nothing stuck at all.
I was planning on flushing the system this weekend and might as well add a new thermostat.
I guess the best thing to do is get the car hooked up to a scanner and that would probably tell me what I need to know...
Thanks Pcolt, I appreciate the Help and suggestions!
Le Mans Master
Joined: Jan 2006
Posts: 5,620
Likes: 206
From: Orlando FL
Temperature wise, it seems like the car is getting to hot too fast. I'm jealous of your cool outside air temps this time of year. Down here in Orlando 90-98 most days in the PM and only 80 or a bit less at night…sucks. Over 95 it's rough in traffic to keep it cool. Was 102 the other day in traffic, temp went to 130 and oil to 145. Finally got on the back roads and got some speed and things came down 20* AND that was with my secondary fan (got a manual switch) running ALL the time….dam.
But with your outside temps you should be doing much better than you are. You might have a tired thermostat causing your higher temperatures. I would give it a flush, new coolant and a LT1 stat. That would be the basic starting place I would go first.
You're not getting opti codes and a scanner will not show you any more than the on board diagnostics will as far as the codes. Opti symptoms vary a lot and there is no one meter, scanner or device that will test or point directly to the opti. After you checked it all out, changed this and that, the opti is the last thing on the list. Substitution is the only sure way to find out. It is a tough job the first time and you have sticker shock. There are worse jobs. The balancer can be the biggest pain if frozen but they all take some work. The rest is not bad, a day or two the first time.
If you go in the opti direction, lots of help on the Forum, common job.
But with your outside temps you should be doing much better than you are. You might have a tired thermostat causing your higher temperatures. I would give it a flush, new coolant and a LT1 stat. That would be the basic starting place I would go first.
You're not getting opti codes and a scanner will not show you any more than the on board diagnostics will as far as the codes. Opti symptoms vary a lot and there is no one meter, scanner or device that will test or point directly to the opti. After you checked it all out, changed this and that, the opti is the last thing on the list. Substitution is the only sure way to find out. It is a tough job the first time and you have sticker shock. There are worse jobs. The balancer can be the biggest pain if frozen but they all take some work. The rest is not bad, a day or two the first time.
If you go in the opti direction, lots of help on the Forum, common job.
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Joined: Jun 2009
Posts: 87
Likes: 0
From: San Diego CA
Wow thats pretty warm in Orlando, im sure it can get pretty muggy and humid too... Cant really complain living in San Diego... lol
Im curious how you wired your 2ndary fan? Ive been wanting to do this for a while just haven't really got motivated to do so, I used to have an 89 Camaro and had my fan wired to a switch inside the car along with a bunch of other mods but not sure how to do so on the LT1's without throwing any codes....
Ill flush the cooling system this weekend and see if that helps, Im sure it will make a difference, Probably even add a bottle or 2 of water wetter by Red line.
Ill probably do everything i can think of before I decide to mess with the Opti...
Im planning on taking my Vette on a road trip to Lake Havasu than to Vegas for Labor day weekend so Id really like to get those temps down and figure out whats throwing the codes...
For some reason its only doing it in closed loop which is also making me think it might be a sensor causing all this, Once it switches to Open loop from Closed the car immediately runs perfect again even after the temps are up...
Im curious how you wired your 2ndary fan? Ive been wanting to do this for a while just haven't really got motivated to do so, I used to have an 89 Camaro and had my fan wired to a switch inside the car along with a bunch of other mods but not sure how to do so on the LT1's without throwing any codes....
Ill flush the cooling system this weekend and see if that helps, Im sure it will make a difference, Probably even add a bottle or 2 of water wetter by Red line.
Ill probably do everything i can think of before I decide to mess with the Opti...
Im planning on taking my Vette on a road trip to Lake Havasu than to Vegas for Labor day weekend so Id really like to get those temps down and figure out whats throwing the codes...
For some reason its only doing it in closed loop which is also making me think it might be a sensor causing all this, Once it switches to Open loop from Closed the car immediately runs perfect again even after the temps are up...
