Electrical system gurus: Need help with ABS issue

[BrianK14]

Ok, long story as short as possible. Bought my 4runner about a year ago with multiple (12) ABS codes showing. I know, I know. I expected it to be a headache. But, low miles, good condition otherwise, and good price. Interestingly, no ABS light or VSC/TRAC lights lit in the dash. In between other upgrades, I've spent a bit of time troubleshooting the prob.

1) Replaced the skid control ECU with a used one from EBay. No improvement.
2) Found two snipped wires in the ECU harness, soldered back. Previous owner did some hackery in the area to install an alarm and remote start, probably related to that. That helped, but didn't solve everything. ABS light and VSC/TRAC lights now on and won't reset. And I'm down to just throwing ABS code 32 (front left wheel speed sensor) and VSC code 43 (ABS malfunction).
3) Wheel speed sensor itself tests good. Also cleaned it up. However, continuity test for harness bad for both leads (double checked my methods by testing the other front wheel speed sensor, found continuity for both leads there)

What's my next step? Seems likely that the previous hackery is likely at fault but I can't find an obvious break in the harness. Anyone have experience with a bad wheel speed sensor harness? Can I bypass the harness? I'm considering temporarily bypassing to see if I can get the ABS codes to reset and the lights out.

[MENTION=10169]TheDurk[/MENTION]



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[Stiles97]

Over the years I have made harness 'bypasses' for testing purposes before tearing out entire harnesses to repair/ replace. I assume from your post if they test 'bad' that you have an open circuit, just want to clarify. I don't have a wiring diagram to reference at the moment but I would give it a try before I tore deeper into the harness. Good luck.

 

[Slowgoat]

You could take the sensor out and clean it. Gunk in there can give a bad speed reading.

Then if that's not it, clean all the connections in the harness going to that sensor.

Then if that doesn't work, take the whole harness out ant try to find a pinched/broken area of the wire by testing sections.

You probably have a section that got crimped or something like that.

Worst case scenario you can just pick up a new speed sensor and harness. I found one OEM for about $50 delivered from amazon.

This is assuming those other broken wires are all fixed up and functioning properly.

I had a problem with mine, same kind of ABS code, and it was a cracked harness at the knuckle. Salt was getting in there. I duct taped it and zip tied it and no problems since.

 

[19963.4lsr5]

My abs problem on the 97 Puppy Hauler was previous owner removed the ABS bulb and one of the rear ABS sensors was bad from torching off a rear shock and taking out the sensor cable.


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[BrianK14]

Goat, I wish it were as simple as replacing the wheel speed sensor. But, my problem is upstream, in the underhood harness of the truck.

 

[Slowgoat]

Aw hell.

There is a short somewhere in the harness.

Not fun to troubleshoot. Now I understand.

 

[BrianK14]

Ok, made some progress. At the wheel sensor end of the harness, further examination found this:

There's my break. Looks as if it were cut. Opened up the harness, soldered, plugged it in. Started the truck and all lights went off by themselves. Didn't even need an ABS code reset. Finally, no trouble codes. An error light free instrument cluster:

However, now I have a new/related problem. The VSC/TRAC is over active. Especially when turning right, power is cut, brakes applied. Hard to take off turning right. Straight or left can cause the same, but much less/milder.

 

[Slowgoat]

Ok, made some progress. At the wheel sensor end of the harness, further examination found this:

There's my break. Looks as if it were cut. Opened up the harness, soldered, plugged it in. Started the truck and all lights went off by themselves. Didn't even need an ABS code reset. Finally, no trouble codes. An error light free instrument cluster:

However, now I have a new/related problem. The VSC/TRAC is over active. Especially when turning right, power is cut, brakes applied. Hard to take off turning right. Straight or left can cause the same, but much less/milder.

Nice!!

Did you unplug your battery for a bit?

Sounds like it may have been malfunctioning and that's why it was cut?? (Previous owner??)

Did you take the sensor itself out and clean it?

There are specific instructions for troubleshooting that sensor in the Toyota Service Manual (dig around, I found it online somewhere.)

Whoever was monkeying with it did something to mess it up, or it should be replaced.

If I remembered right, the abs ring in the hub could be in backwards. You can troubleshoot all of this with a multimeter I'm pretty sure.