There are PLENTY of threads and YouTube videos regarding the 2001 to 2004 EBCM removal. The 1999 - 2000 is different. For one thing, the size and number of Torx screws are different. My car has four T-25 screws, not six T-20 screws.

Please, I am only looking for assistance with the 1999 - 2000 EBCM without active handling, Code M, 09356961 . I owned a 2001 Vette a dozen years ago, and the brake computer was different.

After hours trying to turn the two 10mm insulator nuts on the pump side, I finally did! So far, I disconnected the power connection, removed the four T-25 screws and the EBCM side 10mm insulator nut. The assembly is now up, off the mount, but try as I might, I can not separate the EBCM from the pump assembly.

Since the few used 1999 or 2000 EBCMs that I found for sale online are still attached to the pump side, are they somehow mechanically joined? Or am I just missing something.

Thank you, Bob

 

So this green wire that runs along the top of the pump side of the EBCM, is it suppose to have voltage?

 

There is one bolt at the bottom of the cover with the main electrical connector a 10mm nut just like the sides. Once that is unbolted the whole unit can be lifted up out of the mount. There is a bolt under the rubber isolator, slip the isolator off and then you can remove the bolt.
This needs to come out also, (essentially 5 screws holding the cover on). Now you can separate the module from the pump.

Gary

 

"There is a bolt under the rubber isolator, slip the isolator off and then you can remove the bolt."

Thank you. I had wondered about that. I had the unit up, but couldn't get it apart. But that makes sense.

 

The bolt indicatindicated by #6.

Since I determined by probing the electrical input with a Volt-Ohm meter that the unit is being supplied with battery power, but a scan tool shows no power available to the pump motor, is that indicative of a bad EBCM? When moving, none of the wheel sensors indicated any reading.

See "SW BATT(V)" and "SW PUMP(V)" below.

 

The bolt that holds the EBCM control module to the EBCM pump, is actually a T30 bolt.

 

So, while the EBCM is out, I have been reading about exercising the pump... most of which tell about having the car running on jacks, etc.

I did find a post by The Wrench in 2010 about removing the EBCM and running the pump directly with "10-second passes on the battery charger through a 15-amp fuse."

Where are the contacts to run the pump motor?





??

Thank you.

 

After reviewing some of your previous posts, my assumption here is as follows;
You are working on a 1999 Model year Corvette without active handling option JL4, correct?
You are trouble shooting a DTC fault code C1255, Correct?
If my assumptions are not correct, can you please update the model year and issue you are trobleshooting?
If my assumption is correct, here is some info based on a 1999 model year car with a DTC of C1255.

DTC C1255 EBTCM Internal Malfunction
Circuit Description This DTC identifies a malfunction within the EBTCM. Conditions for Setting the DTC DTC C1255xx is set when an internal EBTCM malfunction exists. Action Taken When the DTC Sets ABS/TCS/Active Handling (if equipped with RPO JL4) are disabled. • Indicators that turn on: - ABS indicator - Car Icon (TCS indicator) • Messages displayed on the DIC: - Service ABS - Service Traction System - Service Active HNDLG (if equipped with Active Handling RPO JL4)

Conditions for Clearing the DTC Diagnostic Aids • Condition for DTC is no longer present and scan tool clear DTC function is used. • Fifty ignition cycles have passed with no DTCs detected. • When DTC C1255xx is displayed on the Scan Tool, it will be followed by two more numbers which should be noted along with any other DTCs that may be displayed. The additional two numbers displayed with DTC C1255xx are for aiding to determine the cause of the internal malfunction. • Make sure the integrity of the connection between the EBTCM and the BPMV is secure, tight, and free from corrosion.
Along with the C1255, a 2 digit Sub Code will set. The first digit is a Letter, and the 2nd digit is a number. Note that only the Tech 2 will display these sub codes, using the On Board Diagnostics through the Drivers Information Center on a Corvette WILL NOT display sub codes.
Here is a list of the Sub Codes that may set: E0, E1, E2, E3, E4, E5, E6, E7 M0, M1, M2, M3, M4, M5, M6, M7 Probable Cause: Each sub code represents a specific malfunction. Most sub codes set due to a malfunction internal to the EBTCM, and can be repaired by replacing the EBTCM. However, EBTCM replacement is NOT always necessary when DTC C1255 is set. Here is a list of exceptions where a fault external to the EBTCM will set C1255. C1255 E2: This Sub Code may set due to a loss of battery or ground to the EBTCM.
1. Battery Cable disconnect
2. EBTCM Fuse Pull
3. EBTCM harness disconnect
4. Weak or Discharged battery
5. Any other interruption of battery or ground to the EBTCM C1255 E2: Can also set when an EBTCM is first installed on a vehicle. C1255 E2 will be stored as a history code only, and WILL NOT turn on the ABS light. A typical service scenario is when an EBTCM is replaced for a DTC other than C1255. The vehicle again returns with the ABS light on, and C1255 E2 is set as a history DTC along with the original DTC which brought the vehicle in for service. The servicing technician is erroneously convinced that the new EBTCM is defective. Replace the EBTCM for C1255 E2 only when a source of a battery disconnect cannot be identified and was not set due to EBTCM replacement. C1255 M5: This Sub Code indicates that the EBTCM has detected a malfunction in the one of the Wheel Speed Sensor Circuits, and sets along with Wheel Speed Sensor DTCs (C1221 thru C1235). Disregard C1255 M5 and perform diagnostics for the other wheel speed DTCs. Only replace the EBTCM if all other wheel speed sensor diagnostics have been exhausted and the source of the DTCs cannot be identified. C1255 E4 and E6 set together: This sub code combination sets when the pump motor ground circuit has detected B+. This condition can occur if the BPMV ground circuit is shared with other components and the ground bolt is loose or disconnected. These other components are seeking ground, then back-feed into the EBTCM thru the BPMV.
Recommendation/Instructions:
if the sub code(s) are included in one of the exceptions listed above, repair the external condition, then clear the code and verify that C1255 does not reset. If the sub code(s) are NOT one of the exceptions listed above, replace the EBTCM.

1999 Schematic

You may have to bolt the EBTCM back in the car, clear completely all the DTC's in the car and do a run down the highway to get the EBTCM to trip-up and post the C1255 code and see if there are any additional DTC codes posted along with the C1255 code for further troubleshooting.
Cheers
Goose

 

This all began in September of 2020. Here it is almost June of 2021, and I have replaced many parts, and though I no longer have code C1255, I get C1233 WHEN THE CAR TRAVELS OVER 30 MPH. Correct, only over 30 mph.

To clear C1255, I purchased a rebuilt ECBM, but it was sealed to the wetside, so it had to be installed at the dealership, to cycle the values when bleeding the fluid.

That was December. I was happy to have fixed the issue... I drove it to work every day for a week, but never went over 40 mph until Saturday, when I took a road trip. To my dismay, at 60 mph, the ABS / TCS lights illuminated. You just don't know how irritated I was. Three monthsand almost $3,000 to "fix" the problem. I read the codes, and found C1233 H, for history. I cleared the codes, and this happened over and over, around 60 mph. I took it back to the dealership for them to read the codes, but was told it was the wheel speed sensor. They quoted $600 to change it.

After stewing a couple more weeks, I started doing research about how to change it myself. I purchased a new wheel speed sensor, swapped it over, and now I get the ABS / TCS lights at 30 mph. I also replaced the 18" harnes, and inspected the rest of the wiring for breaks.

I hooked up a real-time scanner, and drove the car around with a passenger. There is absolutely no interruption in the signal from the replaced sensor, even at and after 30 mph. Nothing wrong. All four sensors read exactly the same, unless the car is turning. Still, the C1233 code illuminates at 30mph, and it won't clear over 30 mph. You must stop the car, turn it off, and then restart it.

Thoughts, before I switch out the wheel speed sensor again? What a PITA, with that one bolt blocked by the ball joint. GM engineers could not think to rotate the three bolts 30 degrees, so this would not be an issue?

Thank you, Bob
​​​​

 

I had a similar code with my 01 except it was C1231 which is left front.

I even bought a new ebcm since a new sensor/hub and the pigtail that plugs into the sensor didn’t fix the problem.

The issue turned out being the terminals on the chassis harness itself that the ABS pigtail plugs into.

I bought a new pigtail and spliced it in.... problem solved. I put the new ebcm on the shelf for a later date.

Here’s the Delco pigtail guide to help you find the part number.
http://www.dstgateway.com/ACDelcoConnectorsV2/#/catalog

 

~Josh, thank you for the information. So, you had a problem where you could drive your car under a certain speed, and the ABS / TCS warning lights would not illuminate? But after reaching a certain speed, it would? And that was caused by the harness between the 18" pigtail and the EBCM?

I could not get the AC DELCO link to open properly on my phone, but what you are saying is that after changing the hub, and the 18" pigtail, I should try changing the next harness between the wheel speed sensor and the ECBM? I am not being sarcastic, but I have searched and searched for someone posting a similar problem, but to no avail.

By way of update, I changed the hub a assembly again today, to a different brand. This time I have until 45 mph before the ABS / TCS warning lights illuminate. I just don't see how this could be purely mechanical, especially when the hub gives the proper speed.

 

Did you replace the sensor with an aftermarket or OEM from the dealer ?

 

The abs sensors themselves don’t typically fail, the terminals loose tension and cause wheel speed codes.

I had a similar issue but mine would work great for an outing, then driving out of my neighborhood it would illuminate. Tried all including a new ebcm and in the end the terminal was it.

Mine wasn’t the only instance, I read about it.... just passing the info.

if you google delco pigtail catalogue you’ll find it. Can search by male/female, how many cavities, and all pictures are color.

 

Since I thought it odd that the different brand wheel hubs would trip the warning lights at different speeds, to recap: I purchased a pair on line, and they both tripped at 30 mph, I purchased a Duralast yesterday, and it tripped at 45 mph, I decided to swap the "bad" right front hub and the "good" left front hub and see what happens.

So, now the right front wheel hub, that I was told was bad, is on the left side of the car, the left front wheel hub, which has worked perfectly fine, is on the right side of the car. And, as predicted, I still get the same warning codes at 60 mph on the right side, but the "bad hub" on the left side does not throw a code. I drove it around for 20 minutes, going a little faster between stops, until I reached 60 and threw the codes.

I find it hard to believe that the next harness in line could be the cause, but it is sure cheaper than swapping ECBMs.

 

I've got the same problem C1233 code. It was setting off at 57MPH. I cleaned the grounds on the frame rails and reassembled with dielectric grease. Also looked at the connections on the short wire loom between the hub and main harness. It looked fine to me. Cleaned them and used dielectric grease during reassembly. Now mine trips the code around 27MPH. Lol!!! Does the harness between the pigtail and the EBCM unplug at the EBCM? If so anyone got a part number for it? I'd rather change the whole harness if it's possible.

 

Hello ramairbrc. Did you find your fix? I have a "late" 98 coupe (EBCM under the hood, looks like yours, 4-screws instead of 6, etc.) and am getting "28-TCS NO COMM,", "SERVICE VEHICLE SOON" blah blah blah. P1571, P1644, & C1780. Also, (pardon my ignorance) do you have to bleed the BPMV/system as a result of separating your EBCM from the BPMV? Great thread. Just what I was looking for, after having read many others. Thanks! Oh, if this gets quashed for some reason, my email addy is turnergt81@gmail.com.

 

FIXED! Many thanks to RedRiderZR1 for the wisdom and support. The EBCM 'capacitor' board had a small explosion. The BIG 820 micro-farad capacitor blew and took the lands on the board with it. Tried to fix it with a new cap & some alternative (pcb) wiring to no avail. Got a 97 Cadillac DeVille EBCM and replaced my 'blown' board with it. No longer have any codes, alerts, or lights on the IPC. It's FIXED! Whoda thunk it? Thanks again RedRiderZR1 and the 97 DeVille!