Just had to ask before i go replacing my ECBM. Is there any connection between the FX3 module and ABS? i know they are in the same location and this car does not have the FX3 module it is supose to. Has anyone pulled their FX3 computer and drover around? I'm sure many have, if you are one of them, did it effect anything? Basically i have false ABS code 25s 32s and 36s, the 25 is LF sensor and it specs perfectly, wiring to ecbm is good. even when i have no service abs light i have no abs. checked the charts in a 91 FSM which should be the same as 90 and have ran out of places to check. ECBM failure seems likely from a voltage spike or something unless FX3 has any influence on the operation.

 

Both the FX3 controller and the ABS get data signals from the vehicle speed sensors (VSS) at each wheel. Vehicle speed plays a part in how the shock stiffness is set by the actuator. Is the SRC light on and do you have any FX3 codes?

You might try and remove each sensor, clean it, and check for any loose connections or broken/frayed wires. Check the connectors for any grease or dirt and the metal tabs for any signs of corrosion.

 

FX3 does not communicate with the ABS period.

 

perfect, that's the anwser i was looking for. as far as the comments on cleaning sensors, it isn't that, the pump doesn't even prime when you start the car. i've grounded the pump with 12v at position 87 and the pump works. either the ECBM is shot or???

 

the fx3 does communicate with the abs ecm but they act separatly. the abs and fx3 wires are combined when you have bots.. sensors data go thru abs ecm first. not the same abs wires and relay when you have fx3. check the sensors relay box behind the left rear whell that is higjtly exposed for any brooken wires.

 

that's my last task before i'm 100% on the ecbm, i've visually looked for broken wires but i need to test the ecbm ground specifically and also it's power source. the pump and relays all have power but it's my last task before calling it. i know the car has experienced a power spike from race track jump starts before i bought it when the car had too small of a alternator pully and would over rpm the alternator frequently. it also would explain why i have no ecbm failure codes, something burned out in the first couple circuts on the way in. i actually may open the box up and see if any parts are visually fried. if so i may be able to order the specific circut from newark and solder it in myself.

 

No they don't but that wasn't what I was getting at. The VSS at each wheel is what provides a signal to both/either the ABS and FX3 systems. If there is a problem with a VSS, there is a possibility of the FX3 system not working properly and possibly setting a code.

Clean the VSS and check all of the VSS connectors for loose or broken/frayed wires.

Electrical issues like voltage spikes can harm the ABS controller but the best way to check that system out is with a scan tool that can run diagnostics on the ABS system.

 

how could the fx3 work properly? i mentioned it being removed in my very first post. i was wondering if the lack of the fx3 module being there would effect the ecbm at all since they share some of the same wiring. bought the car like this you know. one of the vss codes, 25 for example is showing on a brand new sensor i just installed, also traced the wires back to the compartment behind the drivers seat and tested them at the plug, all checks. the real problem here is the abs not firing. the pump should cycle which it does not ever. no signal is getting to the pump relay to ground out. i also replaced that relay lol..basically i have a dead ecbm or a bad signal or voltage to the ecbm. the odd part is not having a ecbm failure code and only false sensor codes. that's the confusing part, false sensor codes after all the hard checks have been done. furthermore the lack of pump cycling has me. the worst part about this task is the normal trouble codes that are so helpful are not helpful anymore lol. once i get that whurr back from the pump on start up my troubles will vanish. that whurr happens from the ecbm sending a signal to the relay to ground, that's not happening in my case. i think GM has a specific scan tool made for tasks like this, probably would help me a great deal. code scan tools bring up the 3 codes i have mentioned, i can't help but wonder if something on the VSS input side of the ecbm got fried. it would explain the codes and also why why i have no hard ecbm failure code. part of the ecbm is working, just not all of it. keep the minds thinking gentelmen, this is probably the hardest electrical grimlin i have faced yet.

 

Missed the part about the FX3 controller being gone :o

If you aren't hearing the self-test, it may be that the ABS pump itself is bad. The self-test requires that the car move thru 4MPH so even if the VSS's are working, a bad pump motor may be why you don't hear the "buzz".

A scan tool like the GM Tech-1 with the brake module installed will allow you to test the pump for proper operation. It's also used to bleed the ABS system when a new pump is installed or a complete fluid flush is done. The pump has to run in order to pass fluid thru the ABS module.

And BTW, ABS pumps are pricey!! A friend of mine had the ABS pump go out on his 90 ZR-1. A GM new pump was around $2K and a reman was over $900 and those were our shop prices He said he can drive without it.....

 

i can get the entire assembly from a wrecked car for 175-200, pump, ecbm relays etc. also there is a way to test the pump and i have done so. on the pump itself there is a bosch relay that trips to send ground to the pump when it gets a signal from the ecb,. if you pop the plastic top off the relay you can use a screwdriver to trip the relay. i did that and magically my whurr sound came on. that was a relief by the way. if your friend needs the pump i'm starting to see a deal form here. i go buy the whole setup for 175, swipe the ecbm and sell him the pump for 100-125. think he would have interest?

 

if you get a complete ABS pump and ECM from another car be very carefull that the car also has the FX3. The abs wires are not the same with or without the FX3.

 

will do, but are you sure the brake modules themselves are different? the factory service manual didn't mention two ebcms, i'm sure i could make certain that i use the same part number already in the car. i wonder if any signals passed through the fx3 going to the ebcm? if so my not having a fx3 module would be a reason. i know there are a ton of wires going to the fx3 clip that just kind of hangout now that it's gone. this thing totally acts like it's either completely fired or something is missing. also a problem i can't find anyone anywhere who has ever had similar issues or solved them.

 

Interesting I roll through the diagrams and there is no interaction with the EBCM from FX3.

They are tied in at #703 wire, but it has no communication capability.



What kind of voltage are you getting at the EBCM as it won't function below 9 volts.

 

LOL the tie at wire 703 is something else, GM uses that black duck tape on top of a solder. i'm going to check voltage at the ebcm wires using the ebcm ground, i've seen weak grounds drop voltage quickly. i'll post the results in a couple hours. if the voltage checks it will push a 90% propability of ebcm failure. hey, maybe this post will be helpful to others in the archives. i'm really set on solving this since not much exists on it out on the web.

 

tonight i have decided to present the inside of one of our ebcm modules. sexy isn't it? on the downside we have a few silicon wafer chips that are basically impossible to eyeball as to if they work or not. on the up side my car now fips the service abs light right on start up with the ebcm out. of course it is supose to do this but i consider that a plus because something changed when i removed the ebcm. now i just have to figure out why no ground is being sent to that black plastic top relay on the abs motor when i start the car {with the ebcm in of course} is the pink white the same color you guys show as a ground to relay? it's dark here now and i live with roomies which means our garage has more than just my tools in it

 

i also found this http://www.automotiveforums.com/vbulletin/t94611.html

it looks like ebcms are famous for similar problems the other way. in my case nothing i do gets that pump going unless i manually fire it up. in this guys case it wouldn't shut off. i think i'm going to harass everyone around my area with a 90-91 vette and try a ebcm swap if i can find a nice enough person to let me steal their unit for 10 minutes.

 

too bad I have a spared module, ecbm, pump and wire here, for 90.....in Paris.

 

Paris would be a long drive, worst part would be that big mud puddle we refer to as the Atlantic, car might get wet

 

bought a ebcm, abs pump, fx3 module and all the relays and wiring from a local wrecking yard for $175 today. they even threw in a couple targa top holder covers. i have my fingers crossed on this one guys ! also i did look at the fx3 cars versus the non fx3. the ebcm is the same and so is the pump. it's the wiring harness that is different. if you were clever and could solder it wouldn't be tough to make a non fx3 harness fx3-able if you had your old one to cut up and splice. the 90-91 ebcm is exclusive to those 2 years and used in both the L98 and ZR1, i did however see the same ABS pump in an 89 so the pump is used in many more years unlike the ebcm.

 

Fixed ! it was the EBCM, now that i can wind this thread to a close i do help it provides some much needed information on EBCM failure and symptoms. The EBCM should show failure codes when it dies, however, mine did not, only ghost codes to sensors that had not failed. The real give away looking back was the ABS pump not priming on start up and the codes randomly showing up, not being set at 19mph like they should be everytime, all the time.