Brake and Service ABS light
Thread Starter
Intermediate
Joined: Apr 2020
Posts: 46
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From: St. Louis, Missouri
Brake and Service ABS light
When driving my 1993 corvette today on the way home, the brake and Service ABS light came on. This used to happend to me for a split second when my fluid wasnt filled all the way to the top due to the sensative level sensor. However this time they stayed on, even after turning the car off.
The codes for module 9 are H64 and H83. I made sure the brake fluid was topped off as it should be. And I have had the H64 code stored before these lights ever came on... any thoughts as to what my issue might be..?
The codes for module 9 are H64 and H83. I made sure the brake fluid was topped off as it should be. And I have had the H64 code stored before these lights ever came on... any thoughts as to what my issue might be..?
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
H64 - Throttle Position Signal Fault
H83 - Brake Fluid Level Low
The first one, if you don't have any errors from the ECM regarding the TPS, is likely a wiring fault with the TPS module located by the blower motor on the passenger side firewall. This is a device that buffers the TPS signal so that the ABS/ASR computer polling the TPS doesn't interfere with the TPS signal going to the ECM. The second one, if you're sure the fluid is topped off, means that the actual fluid level sensor is shot. From the sound of it you already knew that was happening, and it's only just now gotten bad enough to happen often.
If you don't have an FSM for your year, get one. They're like $22 on Rockauto.
H83 - Brake Fluid Level Low
The first one, if you don't have any errors from the ECM regarding the TPS, is likely a wiring fault with the TPS module located by the blower motor on the passenger side firewall. This is a device that buffers the TPS signal so that the ABS/ASR computer polling the TPS doesn't interfere with the TPS signal going to the ECM. The second one, if you're sure the fluid is topped off, means that the actual fluid level sensor is shot. From the sound of it you already knew that was happening, and it's only just now gotten bad enough to happen often.
If you don't have an FSM for your year, get one. They're like $22 on Rockauto.
Thread Starter
Intermediate
Joined: Apr 2020
Posts: 46
Likes: 8
From: St. Louis, Missouri
The brake fluid level issue was only ever on hard braking or cornering, and many others said they had that issue due to the sensor being very sensative.
I dont have any ECM faults that relate to the TPS. I guess ill look into the TPS code more though. It has an H before it, and has been stored the the car since the last time I pulled the codes without any brake warning lights on. So its just odd that it would be the cause of anything now...
I dont have any ECM faults that relate to the TPS. I guess ill look into the TPS code more though. It has an H before it, and has been stored the the car since the last time I pulled the codes without any brake warning lights on. So its just odd that it would be the cause of anything now...
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
The brake fluid level issue was only ever on hard braking or cornering, and many others said they had that issue due to the sensor being very sensative.
I dont have any ECM faults that relate to the TPS. I guess ill look into the TPS code more though. It has an H before it, and has been stored the the car since the last time I pulled the codes without any brake warning lights on. So its just odd that it would be the cause of anything now...
I dont have any ECM faults that relate to the TPS. I guess ill look into the TPS code more though. It has an H before it, and has been stored the the car since the last time I pulled the codes without any brake warning lights on. So its just odd that it would be the cause of anything now...
Last edited by Nomake Wan; May 24, 2021 at 11:51 PM.
Thread Starter
Intermediate
Joined: Apr 2020
Posts: 46
Likes: 8
From: St. Louis, Missouri
ahhh that makes sense. I had read a thread where someone said if it has an H then that means its stored in the history and not an actaul set code, thats why I was confused. Thank you for clearing that up!
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
No worries. 'H' does mean 'Historical' while 'C' means 'Current'. The problem is that you can't have a current code for the ECM when the ECM isn't actually running in normal mode. Same with the ABS. So when you key-on in diagnostic mode, the only computer that can possibly report a 'C' code would be the CCM, since it's the only thing actively polling sensors in that mode.
The only way to see 'current' DTCs from the other computers is to hook a scantool or laptop up to the ALDL port while the car is actually running.
The only way to see 'current' DTCs from the other computers is to hook a scantool or laptop up to the ALDL port while the car is actually running.
Thread Starter
Intermediate
Joined: Apr 2020
Posts: 46
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From: St. Louis, Missouri
Well i went outside to pull it into the garage and try and diagnose it today. And now the brake and service abs lights are gone! The traction control has never worked and the service asr light has always been on. Im kind of suspecting a bad EBCM
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
If the EBCM is bad, you shouldn't be able to query Module 9 at all in diagnostic mode. In addition, the ASR Off button shouldn't do anything at all if you push it while the car is in normal mode. Those are pretty good indications that the EBCM is shot.
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Thread Starter
Intermediate
Joined: Apr 2020
Posts: 46
Likes: 8
From: St. Louis, Missouri
Just got back from a test drive. lights came back on after about 15 minutes of normal driving. I shows codes for modual 9, but when searching for modual 9 to clear the codes it can not be found.... Also I can click the ASR Off button and it lights up ASR OFF, however the Service ASR is always on, and I can confirm that traction control has never kicked in since I have owned this car lol
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Just got back from a test drive. lights came back on after about 15 minutes of normal driving. I shows codes for modual 9, but when searching for modual 9 to clear the codes it can not be found.... Also I can click the ASR Off button and it lights up ASR OFF, however the Service ASR is always on, and I can confirm that traction control has never kicked in since I have owned this car lol
I'm not convinced your EBTCM is bad. It just sounds like your car has had issues since before you owned it that precluded ASR/ABS from operating properly.
Thread Starter
Intermediate
Joined: Apr 2020
Posts: 46
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From: St. Louis, Missouri
It is possive that I am doing it incorrectly. However I was able to clear module 1 and 4 and I belive I found them by hitting the Trip ODO button, and then ENG MET to reset/read the codes from the specific module. The had an H58 code I wrote down from the past that is no longer stored, and now the only stored codes on 9 are the ones stated above. Thanks you for helping out btw.
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
Thread Starter
Intermediate
Joined: Apr 2020
Posts: 46
Likes: 8
From: St. Louis, Missouri
I now have code H58 now too. Which I have had in the past and came back.
My manual says to clear the code, and that if it comes back, to replace the EBCM.
This is most likely my issue right?
My manual says to clear the code, and that if it comes back, to replace the EBCM.
This is most likely my issue right?
Thread Starter
Intermediate
Joined: Apr 2020
Posts: 46
Likes: 8
From: St. Louis, Missouri
Thank you for all of your help! Sorry for all of the questions lol. Im only 18 years old and am learning on this car as I go.
Do you know the best route of getting that fixed..? do people rebuild them? or should i just buy a new one?
Do you know the best route of getting that fixed..? do people rebuild them? or should i just buy a new one?
Drifting
Joined: Apr 2020
Posts: 1,925
Likes: 610
From: Orange, CA
That I can't help you with. I would recommend contacting SIA Electronics and seeing if they would be able to work on the Bosch 2U EBTCM. They do list ABS modules on their site, but not that specific one...but they do say that even if something isn't listed on their site, they may be able to fix it. So yeah, give them a shot, see if they can fix it for you.
If they can't, I'm afraid I don't know of anyone else who rebuilds our ABS modules, and you can't buy them new. The only places I know that do ABS module rebuilds doesn't do anything older than Bosch 5.3 (1992-1994 is Bosch 2U, 1995-1996 is Bosch 5).
If they can't, I'm afraid I don't know of anyone else who rebuilds our ABS modules, and you can't buy them new. The only places I know that do ABS module rebuilds doesn't do anything older than Bosch 5.3 (1992-1994 is Bosch 2U, 1995-1996 is Bosch 5).