ABS Issue/Anti-Lock Light

[E30Bastard]

Sorry for the lag! I had my sister's Mazda in the garage for a few days for repairs. Now that the E30 is back in its rightful place I can continue with fixing this ABS so I can order me a turbo.

Thanks for your response, here are the answers to your questions:

All 4 tires are new Maxxis 202 195/65/14.
Verified to all be same size.
Air is verified at 32psi all around.
Rear wheel bearings are new and good. Rear sensors are new.
Front wheel bearings are old but good and the front abs sensors are old but good as they trigger the abs light upon motion.

Here are the resistance results:

Passenger side connector pin 1 to abs module - 0 resistance
Passenger side connector pin 2 to abs module pin - 0 resistance

Driver side connector pin 1 to abs module - 0 resistance
Driver side connector pin 2 to abs module - 0 resistance

Driver side sensor resistance - 1.04k
Passenger side sensor resistance - 1.023k

Rear driver circuit resistance tested from abs module connector: 1.04k
Rear passenger circuit resistance tested from abs module connector: 1.023k

The wires, connectors, and sensors appear to be definitively good. Ebay another ABS module?

[2mAn]

BUMP

this man is about to test his ABS as he approaches a cliff at full speed.... ABS NEEDS TO GET FIXED

[moatilliatta]

I have one faulty gkn axle out of the car.

What this mean? 1 of 2 of the new GKN axles you bought were faulty?

[E30Bastard]

I bought two new axles, one started spewing grease of the pressed endcap of the axle rather than the cv boot. The pic I sent was just to show the reluctor ring on the bad axle which is out of the car. I bought a third axle and replaced it along with the wheel bearing for good measure so right now there are two brand new, good GKN axles in there. Here's a link to that thread: https://r.tapatalk.com/shareLink/top...ink_source=app Sent from my Pixel 2 XL using Tapatalk

[moatilliatta]

If you put the axles in after you put new sensors in I would consider looking at the sensors and or replace them, Especially if you had fitment issues. Or testing the old axles.

Start from the begin.


I think some of those pins at the ABS sensor can get glitchy, I was trying to explain to OHM the sensors out connected, Check resistance at computer so you get the whole wheel speed sensor circuit. .

To take some guess work out, I do think the ABS system can be read by this tool. I've used this scan tool at the shop and its blown my mind how well its worked on older cars. You'll need to source the obd 16 pin for the 20 pin round adapter.

https://www.amazon.com/dp/B0090B7M2O/ref=twister_B07S2Y6SMW?_encoding=UTF8&psc=1

[E30Bastard]

I did test the whole circuit and the sensors were replaced after axle swap. Please see previous test for circuit test results! I will check out that tool but the abs on e30 is standalone so obd scan wont see it?? Sent from my Pixel 2 XL using Tapatalk

[moatilliatta]

Looks like it is a closed system...

1988 model year 325 page 42 - Id just check all the inputs and outputs after going backwards on what you installed. IE rear sensors and axles.

http://www.wedophones.com/Manuals/BMW/1988%20BMW%20325i%20Convertible%20Electrical%20Troubleshooting%20Manual.pdf

[E30Bastard]

Your link doesn't work. The sensors and wires have been checked. It is definitely something other than the brand new axles, brand new sensors, and verified rear circuits. Sent from my Pixel 2 XL using Tapatalk

[moatilliatta]

Maybe right click and save as or open in new tab, maybe its getting blocked.

New parts can be bad.

[E30Bastard]

Hmm, I have 4 new sensors...same behavior with all. I was thinking about jacking up the car and putting it in first to see what the sensor puts out when wheels spin... Sent from my Pixel 2 XL using Tapatalk

[2mAn]

Why ABS .... WHYYYYYY

[dasmanschaft012]

silly check, make sure a) theres high resistance between the sensor wires and chassis (maybe somewhere in the body the harness rubbed thru) and b) check resistances between each sensor wire with the control module unplugged to make sure the sensor wires aren't shorted together or pinched somewhere in the cable run.

[moatilliatta]

Did you back probe the ABS pump and computer for 12v and ground?

[2mAn]

https://s14net.vbulletin.net/forum/s...ights-si-board

[E30Bastard]

silly check, make sure a) theres high resistance between the sensor wires and chassis (maybe somewhere in the body the harness rubbed thru) and b) check resistances between each sensor wire with the control module unplugged to make sure the sensor wires aren't shorted together or pinched somewhere in the cable run.

Here are the resistance results:

Passenger side pin 1 to abs module - 0 resistance

Passenger side pin 2 to abs module pin - 0 resistance

Driver side pin 1 to abs module - 0 resistance

Driver side pin 2 to abs module - 0 resistance

These wires run from underneath the rear seat directly to the ABS module. They test perfectly and have been ruled out.

Driver side sensor resistance - 1.04k

Passenger side sensor resistance - 1.023k

These are the two sensor wires that run from the connectors underneath the rear seat through the firewall and to the rear hubs. These brand new sensor wires have been inspected multiple times and tested multiple times. They are good.

Rear driver circuit resistance tested from abs module connectors/pins: 1.04k

Rear passenger circuit resistance tested from abs module connectors/pins: 1.023k


This is testing the entire circuit at the ABS module itself, getting the same reading as I did from the sensors alone again means the wires running to the ABS module are perfect.

Some notes/observations:

I can make the light trigger with either of the rear sensors plugged in if i make a slow uturn or i go in reverse and toy with the clutch so as to make the rear end hump or stutter. The wires are 100% good, so what physical issue with the axles or diff would cause this? I just replaced a GKN axle with a chinese axle just to try something else to see if that would make the light come on and I have the same behavior.

It is now pouring rain and I could really use ABS. I've pretty much exhausted everything I can test on this simple, standalone system.

Any suggestions aside from electrical problems (which I have determined through 5 different ABS modules, 4 new rear sensors, and extensive electrical testing to not be the case)?

Much appreciated!!!

P.S. Edit - Just to reiterate - if I plug in either of the front sensors, the light triggers as soon as I start rolling forward. Expected and correct behavior per the Jlevie spin test. The pump and the computer are getting voltage. And just for good measure all relays at the pump and underneath the dash have been replaced with new relays.