Anyone have access to ABS Codes for 95 Miata?

[Mark]

Hello friends. I'm pretty sure that I've got a sensor that has gone bad. Within the first half mile of driving, the ABS kicks in on a normal stop with dry pavement. I can't tell which wheel it is hitting but it can sure make it interesting if you're not ready for it as I lose almost all braking ability. I about smacked the rear end of someone one day when the road was just a little damp. Had to take evasive action to the shoulder! Since then, I've been running without the ABS fuse in the car. It still stops great but I'd really like to fix this.

Anyways, I found plenty of places on the Internet that explain how to read the codes. Just none that can explain what they mean. So if anyone here has a factory service manual or whatever it is where they keep these, I'd sure appreciate a little help.

ABS Codes 11, 51, and 53.

Or the other approach is to find a place that would have a salvaged Miata and buy all four sensors and take the shotgun approach. NAPA shows different sensors at each corner and they run about $280 a piece so doing the shotgun with new parts would be costly.

Thanks,

[bogey]

From a 96 FSM:

11: WSS, SR (RH-Front) - Open or short, Defect

51: Fail Safe Relay - Open Short or Defect

53: Motor, Motor Relay, Open short or Defect


Troubleshooting steps for 11: (Most answers are "Looks OK to me!")
Is ABS CM connector connected properly?
Is wiring harness between ABS CM and Wheel Speed Sensor OK?
Is ABC Wheel speed sensor OK?
Are there missing or damaged teeth on the sensor rotor?
Is the brake line OK?
Is ABS Hydralic Unit OK?
Erase Diagnostis codes and drive car 10MPH, does code come back?

Error 51:
Is BTN Fuse 40A OK/
Inspect valve relay including harness
ERase codes and see if they return.

Error 53:
With IG SW OFF, is motor operating? (as opposed to the engine!)
Is ABS fuse 30A OK
Inspect motor replay including harness
Erase codes and cross fingers

Basically if you don't answer OK to the above items, replace it.

I have specifics on how to test each item, but it is another 10 pages. It details all the resistants on the connector plugs and procedures for testing. I can scan the pages and send them if you need them.

[Mark]

AWESOME! Now I've got someplace to start.

I'm not too worried about the 51 and 53 as I've been driving around with the fuse pulled just so it would be safe. I think if I were to clear the codes and then drive with the fuse in, I'd probably only get the 11 code for right front sensor. If it isn't too much trouble, I'd like to know what the resistance values would be for the sensor.

Tomorrow I pull the wheel and take that baby apart and see what I can find.

Thanks again Bogey!!!!!

[bogey]

Here are the basics of checking the wheel sensor.

Clearance between sensor and sensor rotor: 0.3~1.1mm

Unplug the sensor and check resistance: 0.8~1.2 k ohms

Check the voltage on sensor when unplugged. rotate the hub assembly and it should show 0.25~1.2volts

[Tom @ Fast Forward]

I love this forum. :) None of the crap, just straight answers.

[bogey]

HAH! Fooled you! I made is all up! I am just in it for the post count!

[bogey]

Posts are like green stamps. How many do I need to trade in for a timing controller?

[Tom @ Fast Forward]

You're only 2400 behind. Get busy.


HAH! Fooled you! I made is all up! I am just in it for the post count!

[bogey]

Ok !!!!!!!!!!!

[bogey]

Who Hoo! 10% there!

[Mark]

Well I think I'm pretty much back to square one. I checked both front sensors and they checked out perfectly. Now I'm wondering if the 96 fault codes are different than the 95. The 95 is 3 channel and I think I found somewhere that the 96 is 4 channel. I was able to check one of the read sensors but the other is buried behind the roll bar tube. PITA to get to.

For grins I cleaned all the connectors I could easily get to and test. Put it all back together to see if maybe reseating the connectors might have helped. No dice. ABS pulsing at a rolling 5 MPH stop, and then the light comes on solid. ABS shut itself down.

[bogey]

I do not have a 95 Factory Service Manual, but I would be surprised if things changed in the 95-96 model year. I have not heard of this difference.

Did you compare all the sensors to each other? Is one different than the others? If you can verify that all 4 sensors and wiring are good (at least the same), it is time to move to the ABS relay and motor.

What about the wiring harness to each wheel? Could one of the lines be grounding out before getting to the ABS relay?

Have you disconnected the ABS controller and reseated it? (This must be done with ignition off)

[bogey]

ABS Motor diagnotics test:
- Ignition off
- Disconnect ABS controller module
- Measure resistance between ground and connector "X". Should be 1ohm max.

ABS Connector diagram:
6 connections - smaller connections in middle - 7 connections
Longer edge: A B C D E F - g through u - V W X Y Z AA AB
Shorter edge: AC AD AE AF AG AH - ai through av - AW AX AY AZ BA BB BC

ABS Motor:
- At the ABS Motor, disconnect the 2 pin and measure resistance on pin B.
- Should be 1ohm max. (B is the left connector when the bump keys are up)
- Verify motor runs when applying 12v to "2 pin" (I don't know where "2 Pin" is, it is not labled)

[bogey]

Solenoid Valve Relay:
- Disconnect 12 pin connector from ABS unit.
- Apply 12 volts between terminal A and D (Don't know which is positive vs GND)
- Then measure resistance between terminal B and H, I and J - should be 4.25 ~ 4.75 ohms
- Measure resistance between Terminal B and M, N and O - shold be 8.5 ~ 9.5 ohms

Connector Diagram:
M J - D A
N - H - B
O - I - C

[Tom @ Fast Forward]

94-95 were still OBD-1. 96+ are OBD-2. Very different computers. The codes could have changed? I searched and searched the web and found nothing.

[bogey]

The codes may have changed, but I doubt the ABS mechanicals would be different...

[Tom @ Fast Forward]

I hope you are right because I found nothing useful on the web.

[bogey]

Also, weren't the later 95s (95 1/2s) the first of the OBDII cars? I thought it was a mid year change...

I guess Mark can check for an ODBII connector. It would be just under the edge of the dash to the right of the steering wheel.

[Tom @ Fast Forward]

The ECUs on the 90-95 had two connectors. The ECUs on the 96-00 have three connectors. His car should have an ECU with only 2 connectors. The change came with OBD-2.

[Mark]

Definitely OBD-1. And fairly certain the ABS is 3 channel. 2 hard lines plumbed into the back of the unit near the firewall (suspect supply and return brake fluid), and 3 hard lines plumbed on the top of the unit. One large connector on the front of the unit, underneath a tie-wrapped boot.

I still have 1 sensor to get at. The left rear is stowed up behind my rollbar and the gas filler and vent are in the way of getting my hands in there. The other 3 corners all measure a resistance right around 1050 ohms, plus or minus a few. I switched the meter over to volts and spun each wheel and I'm getting a voltage that is similar at each wheel. It all depends on how fast you spin the wheel. Note that as expected, it is also an AC voltage and not DC.

Kind of humbling! You have the skills to put a whole suspension on the car. Supercharger install goes fairly smooth. Roll bar install a breeze. Top replacement done in a day. Tackle a brake problem? Black magic/Voodoo :(

[bogey]

The 96 is also a 3 channel ABS unit. There is only one hard line to the rear that is shared by both calipers.

Good luck on diagnosing this one... Chances are replacement of the ABS unit is the only solution as it is probably not a servicable part.

I wonder how hard it would be to remove ABS from the car? What would be involved? Can you just leave it disconnected/fuse pulled without any issues?

[Mark]

Without the fuse in, it just acts like a normal braking system with the internal valves in an open position. And the dash light stays on. And the loose nut behind the wheel needs to hone his threshold braking skills along with knowing the different stopping powers of street/race tires! :)

I've got a local mechanic that is just getting started. He gave me a very fair price for installing my clutch parts. I may swing by his shop and see what he has to say about all of this.

[bogey]

I don't have ABS on either of my Miatas and have never felt the need for it. Panic stops have always been well controlled with little/no wheel lockup.

[Mark]

Thanks again Bogey for the information! I ended up taking it into my local mechanic. He put his scan tool on and found the same errors that I pulled, and had the same diagnostic values you found in the FSM. He reset it with his scanner and took it out for a drive. 51 and 53 cleared as they were probably due to me running without 1 of the ABS fuses in. The 11 code came back with just 1 stop, indicating wheel sensor problem.

I had measured the resistance and the voltage generated and I could not find any difference between the left front and the right front. But apparently there must have been something different. He replaced the sensor on the right front, took it out for a drive, and all is well!

[bogey]

At least the diagnostic codes work. I figured the 51/53 were from running without a fuse. Code 11 pointed the right way. How much did the sensor set you back?

[Mark]

I first checked the local Napa and and Advance Auto. Both of them were right around $270. The dealer wanted $205. But the closest dealer to us only orders parts once a week and then they would mail it to the shop, getting here some time next week. :(

So I called Mazmart and they had one at $125.00. It's used obviously, but it works fine in my car!

[bogey]

Such a deal! Used parts are great. I have bought (and sold) several over the past year and have never had a problem.