ABS LIght

[inkjunkie]

The ABS light on our 99 Explorer has been popping on every now and then for several years now. When it first started I plugged my laptop in and took a look for codes using the Auto Enginuity software. No codes. Noticed that if the roads were slick just about guaranteed that the ABS light was going to be on. Just forgot about it.
Last week someone cut my wife off. Light came on. And stayed on. Was running errands the other day in the Explorer and happened to be driving past the NAPA I deal with. Grabbed a rear axle sensor while I was there, figure at 250+k miles it would not hurt to replace it. Plugged my laptop in, sure enough there was 2 codes, C1230 & C1237. Been short on time, did not bother researching either one, just figured I would replace the sensor and see what happened.
Well....the C1237 is now gone....however the C1230 is still there...and the light is on. I have an ALLDATAdiy account so I took a look. In order to troubleshoot it looks like I will be needing a EEC IV breakout box.
Any way around this? Any particular thing I need to be looking for? The harness going to the rear axle sensor doesn't have any mice damage, at least where it is visible.
Any suggestions/input would be greatly appreciated.
One thing I will be doing tomorrow, time permitting, is pulling the sensor back out and cleaning the sensor mounting area on the rear axle thoroughly.

 

[J_C]

Does the Auto Enginuity software show ABS wheel speeds? This should tell you if a valid signal is coming from the rear sensor. If it doesn't show that function, do you know what hardware your OBDII dongle is based on? If it's ELM327 compatible you may be able to use Forscan (free version) on a windows laptop or an android device (whatever your OBDII dongle can connect to), which can show the wheel speed data.

Supposing it is the rear speed sensor signal (also based on the C1230 code), you could measure for mV range AC voltage with a multimeter at the ABS control module on the light green/black and the red/pink wires. These should be the same wire colors going to your rear speed sensor. Of course the vehicle needs to have the rear wheels (differential at least) spinning to get that reading.

Without spinning the differential for a mV AC multimeter reading you can still use an extension lead on the multimeter to measure for continuity between the ABS control module wires mentioned above, and at the rear sensor connector. If there's a break in the wire, as you'd expect, you need new wire. I assume you inspected the sensor wire connector to make sure it isn't corroded inside. Normally the connectors have a plug in them that will slip out then you can pull the wires out for better access to clean the contacts, though working with old plastic connectors, beware that they can be brittle.

I suppose it's possible the sensor ring in the differential is gunked up but I don't have any advice for resolving that, other than that it's probably also a sign you need to replace the differential fluid. I mean sure, you can pull the differential apart enough to replace that ring "IF" it's the problem but I have never done that and can't advise on it, and it seems like the most intrusive and time consuming thing to do so it would be my last resort and I feel it's more likely electrical than that.

 

[inkjunkie]

Does the Auto Enginuity software show ABS wheel speeds? This should tell you if a valid signal is coming from the rear sensor. If it doesn't show that function, do you know what hardware your OBDII dongle is based on? If it's ELM327 compatible you may be able to use Forscan (free version) on a windows laptop or an android device (whatever your OBDII dongle can connect to), which can show the wheel speed data.

Supposing it is the rear speed sensor signal (also based on the C1230 code), you could measure for mV range AC voltage with a multimeter at the ABS control module on the light green/black and the red/pink wires. These should be the same wire colors going to your rear speed sensor. Of course the vehicle needs to have the rear wheels (differential at least) spinning to get that reading.

Without spinning the differential for a mV AC multimeter reading you can still use an extension lead on the multimeter to measure for continuity between the ABS control module wires mentioned above, and at the rear sensor connector. If there's a break in the wire, as you'd expect, you need new wire. I assume you inspected the sensor wire connector to make sure it isn't corroded inside. Normally the connectors have a plug in them that will slip out then you can pull the wires out for better access to clean the contacts, though working with old plastic connectors, beware that they can be brittle.

I suppose it's possible the sensor ring in the differential is gunked up but I don't have any advice for resolving that, other than that it's probably also a sign you need to replace the differential fluid.

The Auto Enginuity software does indeed show ABS wheel speeds.
The plug on the rear axle speed sensor was spotless. It is missing one ear...so the sensor was replaced before we bought the truck.
Forgot....changed the diff fluid about 8k miles ago. Everything looked pretty clean...

 

[inkjunkie]

Can't believe no one else has ran into this....

 

[inkjunkie]

Both wires going to the rear Speed Sensor were partially broken, right at where the clamp closest to the frame is. Looks like they may have been a spring holding tension on the e-brake cable that is now busted. The wires are clamped to the e-brake cable so without the spring they are forced to flex quite a bit.

 

[J_C]

Good to hear you found it. I'd probably go the easy route and just splice in wire at the damaged area and use (hot) glue lined heatshrink tubing to seal it.