4th Gen - Strange 4WS Issue

[arif_manji]

Hi Guys,

I have a strange issue with my 4th Gen 4WS system. 4WS error code 36 and ABS error code 44, rear right side ABS speed sensor. As I was desperate for one due to MOT, I the sensor out of my other 4th Gen which has a fully working 4WS system. To be sure, I took it for a drive before removing the sensor and fitting it into the troubled Prelude.

Oddly, getting the same error code. I have reset the system by disconnecting the battery and leaving it for 20 minutes, same issue.

I've never seen this issue before. I'm starting to think this might be a ABS ECU or 4WS ECU issue. Has anyone else had this issue before?

Any advise will be appreciated.

Thanks

[Scott560]

I'd start with the basic checks.

Check for continuity from the wheel well plug back to the abs ECU multiplug. The wire could simply have a break in it.

Unplug the ABS loom from the ECU and check for lack of continuity to ground, the cable could be shorted out in a rusty bracket somewhere or trapped during recent work. Check there is no continuity between the pair of wires when the sensor and ECU is unplugged also, they could be bridged by corrosion,pinching or worn insulation etc.

If you have access to an oscilloscope, check that you have a waveform from the sensor unplugged and plugged whilst you spin the wheel, the reluctor ring could be cracked or misaligned from rust

After that, I'd look for damage inside the ECU caused by cracked solder joints or water intrusion at the loom multiplug.

Good luck!

[vanzep]

Im no use when it comes to electrical stuff in the lude so when i got a weird abs/4ws code I changed the 4ws ecu and that cleared it - bit of pain getting the ecu out of the boot as it seems to have many bolts holding it in place - check and clean the earthing wires as well.
If you have a spare 4ws ecu that would be good.
just out of interest have you had any alternator/battery warning lights at any time ?

[arif_manji]

@Scott560 Thanks mate, I've been looking through the Honda manual on how to do this so will give this a try when the weather is better.

@vanzep Thanks mate, I did swap over the ABS ECU = same issue, 4WS ECU = same issue. I even replaced the sensor again that I had spare, it was for the left side. Same code. I think I purchased a set of four from you a few years ago! I only ever used the rear right one for another Prelude.

I think @Scott560 might be right, it seem to be an connectivity issue. The sensor plug accessibility isn't great so will need some time to get the car jacked high enough to do some tests. But ill do the internal ABS ECU plug tests tomorrow. The ABS ring looks like in good condition, in fact very clean.

Another question for you guys, the 2 x bolts that hold down the sensor to the hub, do those bolts earth the sensor at all? It looks like in the past its had a replacement sensor but one of the bolts had snapped and is only fastened down with one. Not sure if that would cause issues?

I'm so surprised it was left like this as its been maintained and serviced by Johnsons Honda in Milton Keynes all of its life. I bought it from an elderly couple who bought it from new and who also lived in the same town as me. I use to supply the couple with parts when Honda discontinued most parts. Sadly Honda said they will no longer work on the car due to the age. It's then that I bought it from them last week.

It's an extremely clean Milano Red UKDM 1996 2.2i VTEC - its like brand new to be honest hence why I'm so surprised of this issue.


upload pic

[vanzep]

That does look very good arif like you say its been very well looked after but being a uk car is bound to have the odd rusty bolt - the sensor ones are notoriously difficult to remove - dont think they have anything to do with earthing.
I remember vtecmec saying it was worth checking and cleaning/re greasing the main connector to the 4ws rack under the car....
I saw you had your burgundy one up for sale

[Scott560]

They don't earth through the bolt. If you thing about it, the suspension components are insulated from chassis by rubber bushings so they wouldn't work as an earth in the electrical sense.

[arif_manji]

That does look very good arif like you say its been very well looked after but being a uk car is bound to have the odd rusty bolt - the sensor ones are notoriously difficult to remove - dont think they have anything to do with earthing.
I remember vtecmec saying it was worth checking and cleaning/re greasing the main connector to the 4ws rack under the car....
I saw you had your burgundy one up for sale

Good idea, I will grease the connector on the 4WS connectors. The burgundy belongs to a friend of mine which I restored for him a couple of years ago, that was a huge project. After a lot money he invested in the car, he has now wanting to sell it. It's a really high spec Prelude too!

They don't earth through the bolt. If you thing about it, the suspension components are insulated from chassis by rubber bushings so they wouldn't work as an earth in the electrical sense.

I did some more tests today. The resistance between rear sensors seemed fine and within the range (Right Side 1256 Ohms - GRN/YEL to BLU/YEL and Left Side 1254 ohms - LT BLU to GRY).

However, the issue seems to be no continuity on the Right Side which would explain the issue I'm having. But I'm confused on how I was able to measure the resistance between that Rear Right side Sensor if there is no continuity on the BLU/YEL and GRN/YEL wires?

I'm not the best at electrics but I usually follow manuals and YouTube videos. Any advise will be appreciated.

[Scott560]

hmm, code 44 is rear left 'wheel lock' according to the 5th gen manual. Eg, it's picking up continuity in the sensor, but not seeing any pulses when the brake pedal was pressed. 43 is rear right (eg, drivers side on UK/Jap car). Humorously, the diag manual says 'the probably cause was the vehicle spun during cornering', clearing it should remove it but I assume you have tried that.

The sensors are just coils of wire. When they are disconnected form the circuit, you should see similar resistance of the sensors, which you do, so I would say the sensors and the first part of the loom (pig tail) is fine. This also bares out as it was taken from a working car.

You shouldn't be getting continuity to ground with the abs ecu disconnected. You might be with the connected but that wont help you work out what's wrong.

1) With Sensors disconnected at the rear of the car, you should get a reading for continuity between the 2 pins of the sensor mutiplug - you do - good stuff, next test...

2) Disconnect the ABS ECU multiplug, and find the respective pins for the sensors, Again, you should get continuity on the pairs of pins that relate to each sensor. The readings will be a bit higher as more wire means more resistance... This confirms that the 2 wires for each sensor are intact front to back of the car.

3) sounds like you might have already performed this one in some way. With the ABS ECU disconnected, check for continuity at the ABS ECU Multiplug loom end between ground and each of the 2 pins that relate to the rear sensors. You shouldn't have any continuity with ground at all. If you do, then a wire somewhere from front to back is pinched/abraded/touching the chassis somewhere it shouldn't.

4) if you can't easily probe the ABS ecu loom connector, then you can perform the same test at the sensor connectors whilst they are disconnected. However, check for ground here is unlikely to reveal a short, as i suspect it would only short to the wheel hub metal. Still worth checking as if i recal the wire is held to a metal bracket that can rust - it could crush/cut through the insulation.

It can be impossible to test some sensors when they are 'in circuit', that is, they are still connected to the ECU.

If all of the above checks out (continuity for both sensors at the rear pig tail, continuity at the front of the car for both with ecu unplugged, and no continuity to ground for any of the wheel sensor pins when disconnected from ABS ECU) then I would probably say you have a fault within the ABS ECU. It could just be cracked solder joint inside the ECU, but this is a fault normally seen on the 4ws ecu due to high power switching and thermal/physical stresses caused by large connectors.

Hope that makes sense - also hope that the 5th gen codes are similar to the 4th gen as it might explain why your replacement sensor didn't fix it, it could be the wrong sensor you have been focusing on.

[arif_manji]

hmm, code 44 is rear left 'wheel lock' according to the 5th gen manual. Eg, it's picking up continuity in the sensor, but not seeing any pulses when the brake pedal was pressed. 43 is rear right (eg, drivers side on UK/Jap car). Humorously, the diag manual says 'the probably cause was the vehicle spun during cornering', clearing it should remove it but I assume you have tried that.

The sensors are just coils of wire. When they are disconnected form the circuit, you should see similar resistance of the sensors, which you do, so I would say the sensors and the first part of the loom (pig tail) is fine. This also bares out as it was taken from a working car.

You shouldn't be getting continuity to ground with the abs ecu disconnected. You might be with the connected but that wont help you work out what's wrong.

1) With Sensors disconnected at the rear of the car, you should get a reading for continuity between the 2 pins of the sensor mutiplug - you do - good stuff, next test...

2) Disconnect the ABS ECU multiplug, and find the respective pins for the sensors, Again, you should get continuity on the pairs of pins that relate to each sensor. The readings will be a bit higher as more wire means more resistance... This confirms that the 2 wires for each sensor are intact front to back of the car.

3) sounds like you might have already performed this one in some way. With the ABS ECU disconnected, check for continuity at the ABS ECU Multiplug loom end between ground and each of the 2 pins that relate to the rear sensors. You shouldn't have any continuity with ground at all. If you do, then a wire somewhere from front to back is pinched/abraded/touching the chassis somewhere it shouldn't.

4) if you can't easily probe the ABS ecu loom connector, then you can perform the same test at the sensor connectors whilst they are disconnected. However, check for ground here is unlikely to reveal a short, as i suspect it would only short to the wheel hub metal. Still worth checking as if i recal the wire is held to a metal bracket that can rust - it could crush/cut through the insulation.

It can be impossible to test some sensors when they are 'in circuit', that is, they are still connected to the ECU.

If all of the above checks out (continuity for both sensors at the rear pig tail, continuity at the front of the car for both with ecu unplugged, and no continuity to ground for any of the wheel sensor pins when disconnected from ABS ECU) then I would probably say you have a fault within the ABS ECU. It could just be cracked solder joint inside the ECU, but this is a fault normally seen on the 4ws ecu due to high power switching and thermal/physical stresses caused by large connectors.

Hope that makes sense - also hope that the 5th gen codes are similar to the 4th gen as it might explain why your replacement sensor didn't fix it, it could be the wrong sensor you have been focusing on.

Hi @Scott560.

I've double checked the code, it is definitely ABS = 44 and 4WS = 36. The OEM manual also shows it as the rear Right side Sensor?





Just to clarify to point 1) I did the test with the ABS ECU unplugged but the ABS sensors were still connected. Also on point 3), I get continuity to the ground but for the left sensor GRY wire. I have also tried a replacement ABS ECU and get the same error and results.

This is mind boggling. I think I need to get under the car and have a look at the ABS plug.

[wurlycorner]

With the connector unplugged at the ECU (as you tested it before) check LT BLU to ground and GRY to ground. Should be infinity - if it's not then you have an earth leak fault somewhere and that will be dragging the signal down, even though the sensor and wiring itself bell out individually ok.