4th Gen - Strange 4WS Issue

[arif_manji]

Hi @wurlycorner,

I checked this morning, there is continuity on both LT BLU and GRY wire. I'm starting to think the rear left side sensor maybe causing this or there something shorting out that side?

It's odd that the error code is showing for the the rear right side sensor but wiring for the rear left has continuity? I'm confused.

[wurlycorner]

Hi,
I'm confused what do you mean when you say it has continuity? Continuity from where to where?

[arif_manji]

Hi @wurlycorner, apologies I probably didn’t explain well. There is reading from;

- LT BLU to Ground
- GRY to Ground

The other sensor pins don’t nothing coming through?

[Scott560]

Hi @wurlycorner, apologies I probably didn’t explain well. There is reading from;

- LT BLU to Ground
- GRY to Ground

The other sensor pins don’t nothing coming through?

Is this with the ecu or sensors unplugged?

If either of those pins have continuity to ground whilst the ECU is disconnected, then there is a problem with the wiring somewhere, it will have been chafed through or clamped somewhere by accident?

By continuity, we mean that the circuit is complete, eg, your tester is making a beep noise (as if you touch the 2 test leads together)?

[arif_manji]

Hi @wurlycorner, apologies I probably didn’t explain well. There is reading from;

- LT BLU to Ground
- GRY to Ground

The other sensor pins don’t nothing coming through?

Is this with the ecu or sensors unplugged?

If either of those pins have continuity to ground whilst the ECU is disconnected, then there is a problem with the wiring somewhere, it will have been chafed through or clamped somewhere by accident?

By continuity, we mean that the circuit is complete, eg, your tester is making a beep noise (as if you touch the 2 test leads together)?

This is with the ECU unplugged but with sensors plugged.

I’ve taken pictures as I maybe causing confusion to you guys - the DC voltage is only on those two wires (the rear left side sensor) no other sensors pins have readings.





What do you guys think?

[Scott560]

Your meter is not setup correctly and you are not performing the right test. With the meter as pictured, you are currently measuring for voltage, but your probes/leads aren't even in the right holes either for measuring voltage so that's a non-starter. You will always get a slight spurious reading of voltage when the probes are not connected (as yours are not connected properly). You would not expect any voltage on the 2 sensor pins unless the wheel was spinning.

Your meter needs to be put onto the Red Diode/Continuity mode (diode symbol and buzzer, just short of 6 o'clock). And your black probe needs to be in the middle 'Com' (Common/ground) hole. Your red probe can stay on the right side (Notice it has a V , to measure voltage, and an ohms symbol for resistance/continuity). Once you have the black in the middle, red on the right hand side, and the dial turned to Red Diode/Buzzer symbol - you should be good to do a continuity test. Press the 2 test probes together, it should beep, confirming continuity (A complete circuit) between the 2 probes.

You can then do the tests as described above - checking that you have continuity on the 2 wires for each sensor, front to back (ecu unplugged, sensors plugged). Once that's done and confirmed, pop the black onto the chassis electrical ground point somewhere, and then a probe in each of the ABS sensor wires at that multiplug. If you hear a beep, then one of the abs wires has been pinched/trapped to ground somewhere, or insulation rubbed/gnawed off).

If there is continuity between the 2 sensor pins, but not on any of the pins to ground, then id say its starting to look like the ABS ecu...

Of course you are free to try some other tests - check if you can measure voltage on the 20v scale whilst an assistance spins the wheel. This would help confirm the sensor is situated correctly but I know you are experienced enough to be sure if it wasn't sitting flush enough or close enough to the abs ring (and also sensor is known good, removed from working car). I have had once, on a different car, the wrong driveshaft and abs ring fitted, that caused no end of ABS grief but not these symptoms. Worth double checking the alignment in case the ring was disturbed at some point (wheel bearing replacement perhaps?)

Hope that helps!

[arif_manji]

Your meter is not setup correctly and you are not performing the right test. With the meter as pictured, you are currently measuring for voltage, but your probes/leads aren't even in the right holes either for measuring voltage so that's a non-starter. You will always get a slight spurious reading of voltage when the probes are not connected (as yours are not connected properly). You would not expect any voltage on the 2 sensor pins unless the wheel was spinning.

Your meter needs to be put onto the Red Diode/Continuity mode (diode symbol and buzzer, just short of 6 o'clock). And your black probe needs to be in the middle 'Com' (Common/ground) hole. Your red probe can stay on the right side (Notice it has a V , to measure voltage, and an ohms symbol for resistance/continuity). Once you have the black in the middle, red on the right hand side, and the dial turned to Red Diode/Buzzer symbol - you should be good to do a continuity test. Press the 2 test probes together, it should beep, confirming continuity (A complete circuit) between the 2 probes.

You can then do the tests as described above - checking that you have continuity on the 2 wires for each sensor, front to back (ecu unplugged, sensors plugged). Once that's done and confirmed, pop the black onto the chassis electrical ground point somewhere, and then a probe in each of the ABS sensor wires at that multiplug. If you hear a beep, then one of the abs wires has been pinched/trapped to ground somewhere, or insulation rubbed/gnawed off).

If there is continuity between the 2 sensor pins, but not on any of the pins to ground, then id say its starting to look like the ABS ecu...

Of course you are free to try some other tests - check if you can measure voltage on the 20v scale whilst an assistance spins the wheel. This would help confirm the sensor is situated correctly but I know you are experienced enough to be sure if it wasn't sitting flush enough or close enough to the abs ring (and also sensor is known good, removed from working car). I have had once, on a different car, the wrong driveshaft and abs ring fitted, that caused no end of ABS grief but not these symptoms. Worth double checking the alignment in case the ring was disturbed at some point (wheel bearing replacement perhaps?)

Hope that helps!

Hi @Scott560,

Thanks for the clarification, I did have doubts on what setting I had it on.

So I’ve followed your advice and re-tested all four sensors. They have the correct resistance and are within the ranges (rears are; 1297-1299 and the fronts 980-982).

But there is no continuity to those pins to ground. So I tried the same tests on two other ABS ECU’s (facelift and non facelift ones as I had both) and have the same result.

If it’s not the ECU, what else could it be?

[Scott560]

Does the abs issue go away when you use a new ECU?

Im not sure I follow what you mean by you did the test with some other ECUs, the ECU is supposed to be unplugged lest it interfere with the circuit you are testing.

If the sensor is physically installed fine, sensor is confirmed working, and the abs ring looks like it's the same as the other side and in the right place, and the wiring checks out fine as it does, then it sounds like it really could be the ECU.

With the car jacked up, you can physically see the abs ring turning with the wheel? It's not stuck with rust and just spinning on the hub?

You can do more tests, check for voltage at the sensors with the ECU unplugged , you should get something whilst the wheel turns. You can't check it fully, but it would help rule out any issue at the sensor/ring end.

End of the day, the ECU thinks the rear wheel is not turning during braking or the car has spun, so starting to sound like ECU to me.

When did the fault occur, just randomly ordered after some work?

[arif_manji]

Does the abs issue go away when you use a new ECU?

Im not sure I follow what you mean by you did the test with some other ECUs, the ECU is supposed to be unplugged lest it interfere with the circuit you are testing.

If the sensor is physically installed fine, sensor is confirmed working, and the abs ring looks like it's the same as the other side and in the right place, and the wiring checks out fine as it does, then it sounds like it really could be the ECU.

With the car jacked up, you can physically see the abs ring turning with the wheel? It's not stuck with rust and just spinning on the hub?

You can do more tests, check for voltage at the sensors with the ECU unplugged , you should get something whilst the wheel turns. You can't check it fully, but it would help rule out any issue at the sensor/ring end.

End of the day, the ECU thinks the rear wheel is not turning during braking or the car has spun, so starting to sound like ECU to me.

When did the fault occur, just randomly ordered after some work?

When I say tested with 2 other ECU’s, I mean I swapped them over one by one and carried out the same tests with the 20 pin plug disconnected. The tests shows no continuity with ground. I then drove it down the road, same codes.

I purchased this Prelude with this issue from an elderly couple who bought it from new. The Honda dealership has looked after the car ever since. They couldn’t figure out the issue with the ABS/4WS issues.

I will check the ABS rings later, I’ll double check the ABS sensors (resistance test) etc too.

[arif_manji]

So in my lunch, I went out and took both rear wheels off to do some more checks.

The ABS ring looks clean and spins absolutely fine.



Also checked the resistance in the sensor, within range and looks fine too.



While I was under the car testing the ABS loom plug, I notice due to the snapped sensor remaining stud bolt, the sensor sits a little proud, I’d say 1-2mm? Would that cause the issue? I didn’t notice this before due to the angle I was removing and fitting it.





Thoughts?