trifecta lights with no speedo & MPG gauge

[Loperamide]

I have changed the rear left wheel speed sensor with a brand new Pagid brand, however the trifecta lights returned after some driving.

The speedo also stops working at the same time.

What could be causing this?

2003 4.4i

[X5Sport]

Assuming the sender is OK then it could be a wiring issue as in poor/dirty/broken connection at wherever it plugs in. Water ingress in the connection is a possibility - might cause a short or open circuit.

If it was working then I’m just brain dumping options at present.

Clear the code and see what comes back?

[Loperamide]

Assuming the sender is OK then it could be a wiring issue as in poor/dirty/broken connection at wherever it plugs in. Water ingress in the connection is a possibility - might cause a short or open circuit.

If it was working then I’m just brain dumping options at present.

Clear the code and see what comes back?

Thanks for the reply.

The lights don't come on until the car reaches operating temperature. If it was a connection issue then surely the lights would be on all the time?

Once the lights come on, clearing the code does nothing - the lights remain lit.

[Loperamide]

I have attached some more pics of INPA while moving, to see if it would help anyone diagnose this more specifically, and also a short video clip of the Live Data.

https://www.youtube.com/watch?v=y-VPu1zXR0M

[X5Sport]

The speedo is driven from that sensor and it is showing as open circuit. That will cause your speedo loss. Either the sensor is bad, or there is a wiring issue between it and the main electronics. It also drives part of the ABS and DSC hence having all three lights on.

It could be temperature related if the sensor is failing when hot (such as after brakes are used) or something else is causing the wiring to heat up and a bit of expansion is breaking a connection (such as might happen in a damp/dirty connector). It might just be water inside the loom itself giving rise the signal loss because of corrosion and a ‘dry joint’.

It is probably worth opening each wiring connection between the wheel sensor itself and where the wires come into the body and spraying them with contact cleaner. Check that all of the plug/socket contacts are clean (bright metal visible), intact and without corrosion. If the wires are bad then you’ll need a new piece.

I found this.......courtesy bavauto’s blog:

https://blog.bavauto.com/4167/x5-bmw-ab ... always-on/

[Loperamide]

The speedo is driven from that sensor and it is showing as open circuit. That will cause your speedo loss. Either the sensor is bad, or there is a wiring issue between it and the main electronics. It also drives part of the ABS and DSC hence having all three lights on.

It could be temperature related if the sensor is failing when hot (such as after brakes are used) or something else is causing the wiring to heat up and a bit of expansion is breaking a connection (such as might happen in a damp/dirty connector). It might just be water inside the loom itself giving rise the signal loss because of corrosion and a ‘dry joint’.

It is probably worth opening each wiring connection between the wheel sensor itself and where the wires come into the body and spraying them with contact cleaner. Check that all of the plug/socket contacts are clean (bright metal visible), intact and without corrosion. If the wires are bad then you’ll need a new piece.

I found this.......courtesy bavauto’s blog:

https://blog.bavauto.com/4167/x5-bmw-ab ... always-on/

Thanks for the reply.

The trifecta lights come on WITHOUT the car being driven, and left to idle until reaching operating temp (around 105c).

[X5Sport]

I’m clutching at straws here, but that might just be how long the system takes to get bored with waiting for a signal? If you drive off immediately then it works before dropping out once it warms up so something must be happening as the warm temp is hit. It might just be coincidence with the engine temp.

The only other thing that I can think to try is not starting the car (you’ll probably need a charger for this) but having all of the electrics on and the laptop plugged in and see if the left wheel sensor drops off the bus after a certain time. With everything ‘cold’ is it there? That could indicate a wiring issue due to high resistance causing a heat increase as above.

It seems (to me) to be something connected with that sensor/circuit. What happens if you waggle the cables connected to the sensor when static? Does the open circuit warning disappear?

It might not be at the wheel end, but up front wherever that wire resurfaces into the rest of the system.

Beyond that I’m at a loss as to what to eliminate as there are no other error codes.

[Loperamide]

One thing i forgot to mention is the MPG gauge on the cluster also stops working at the same time, however the tachometer, fuel gauge and temp gauge continue to work. Does this help anyone with the diagnosis?

[fenj66]

could you try swapping the right rear sensor with the new left one, just to rule it out

[Loperamide]

could you try swapping the right rear sensor with the new left one, just to rule it out

I will have to try on the weekend when I have time.

[X5Sport]

I have a sneaking suspicion that without the speed data (also used to drive the speedo) the mpg gauge can’t do its calculation so fails too. IMHO there’s something wrong in that circuit, but the puzzle is why the engine needs to warm up first? Unless that’s a complete red herring.

I’ve just had a look at the wiring diagrams on Newtis (not the easiest to work through!). Depending upon the actual production month, the wheel sensor looks to route to pins 13 & 14 (up to 09/03 production) or pins 15, 20 & 33 (09\03 production onwards) of the ABS/DSC module. It is this module that drives the warning lights.

The speedo also gets its data from the ABS/DSC system (from that same wheel sensor) and that is then fed to the instrument cluster.

If swapping the sensor over makes no difference then the connectors on the ABS unit could probably do with a check too. If swapping it fixes it, problem solved

I’m not sure where the ABS/DSC module is relative to the engine but if heat really is having an effect then that suggests having a look at the front end connections on the ABS/DSC unit where the wheel sensor wires arrive. My thought process is simply heat may be showing an error up in/at the module itself, such as I suggested a bad wire, pin, or just (remotely) possibly there is a cracked joint or PCB track. I’ve seen this before as an electronics engineer and it makes fault finding a real challenge, needing use of oscilloscopes to trace the signal from sensor to circuit and then across the PCB. The system would just report a no signal condition (as it is) but that isn’t the actual problem.

[Loperamide]

I have a sneaking suspicion that without the speed data (also used to drive the speedo) the mpg gauge can’t do its calculation so fails too. IMHO there’s something wrong in that circuit, but the puzzle is why the engine needs to warm up first? Unless that’s a complete red herring.

I’ve just had a look at the wiring diagrams on Newtis (not the easiest to work through!). Depending upon the actual production month, the wheel sensor looks to route to pins 13 & 14 (up to 09/03 production) or pins 15, 20 & 33 (09\03 production onwards) of the ABS/DSC module. It is this module that drives the warning lights.

The speedo also gets its data from the ABS/DSC system (from that same wheel sensor) and that is then fed to the instrument cluster.

If swapping the sensor over makes no difference then the connectors on the ABS unit could probably do with a check too. If swapping it fixes it, problem solved

I’m not sure where the ABS/DSC module is relative to the engine but if heat really is having an effect then that suggests having a look at the front end connections on the ABS/DSC unit where the wheel sensor wires arrive. My thought process is simply heat may be showing an error up in/at the module itself, such as I suggested a bad wire, pin, or just (remotely) possibly there is a cracked joint or PCB track. I’ve seen this before as an electronics engineer and it makes fault finding a real challenge, needing use of oscilloscopes to trace the signal from sensor to circuit and then across the PCB. The system would just report a no signal condition (as it is) but that isn’t the actual problem.

One thing I have noticed is, the trifecta come on when im at a stand still and not moving.

[henrym3]

I always thought this was quite a common problem, after fixing/replacing the things that the diagnostics reports and still having the problem the go to place is the ABS module. Dismount and send it off for repair. Unplug, remove the screws (6 I think) Most places give a limited lifetime warranty.

[Loperamide]

I always thought this was quite a common problem, after fixing/replacing the things that the diagnostics reports and still having the problem the go to place is the ABS module. Dismount and send it off for repair. Unplug, remove the screws (6 I think) Most places give a limited lifetime warranty.

Where in the UK can I send it to?

Is the car still drivable without the module, while it is off to be repaired?

[X5Sport]

The car won’t be drivable as the ABS module is part of the braking system.

Have a search on line for BMW ABS Module repairs. There are a few UK specialists.