SLS Fault Codes

Hi guys,

Got a strange fault code that I can’t make sense of with my SLS.

Basically, my 2004 discovery 2 XS had had coil springs retrofitted.

I bought new air pipes, overhauled the compressor with new media and piston ring etc. new height sensors, contitech rear airbags then coded it back in and calibrated the heights etc with my Hawkeye.

I then had wandering rear left height levels, I completely bypassed the original wire assuming it was chaffed somewhere with brand new cable and OEM rear sensor connector plugs this fixed it perfectly.

I now get constant beeping and warning light after a short drive with the following fault code present it was there before touching the wiring also so not related to that:

4140: Rear left (power amp. with short to ground)

Does anyone know what the power amp actually is? Really at a loss now with what to do!

This may well be one for @sierrafery

Hi, just clarify something about the following statements:

Josh! said:

I then had wandering rear left height levels, I completely bypassed the original wire assuming it was chaffed somewhere with brand new cable and OEM rear sensor connector plugs this fixed it perfectly.

Click to expand...

How did you bypass the cable and which "original wire" are you talking about?

Josh! said:

I now get constant beeping and warning light after a short drive

Click to expand...

1. Which warning light?
2. Are all the SLABS related warning lights working on self test?

sierrafery said:

Hi, just clarify something about the following statements:

How did you bypass the cable and which "original wire" are you talking about?

1. Which warning light?
2. Are all the SLABS related warning lights working on self test?

Click to expand...

Hi thank you for the reply.

From looking at the workshop manual etc the 3 wires go direct from sensor connector to SLABS ecu connector.

I bought new OEM connectors and connected that to a length of 3 core 0.5mm2 wire ran along the chassis through the bulkhead then connected to pins 123 on the SLABS SLS connector plug.

All error warning lamps are fully functioning, the one which is illuminating is the orange SLS warning lamp with the up/down arrows.

This fault was present when I initially recoded the system for air before touching any wiring so I don’t think it is related.

The wiring from the sensor doesnt go directly to the ECU it passes through connector C0391/0377 which is in the engine bay but that might not be relevant for the fault i mentioned it only for accuracy ...

did you completely remove the old wires at the ECU plug and pinned in the new ones? .... if yes the ECU is very suspect, the fault code is about the ECU's 5V supply to the sensor cos that "power amp." is an electronic switching circuit within the ECU which acts as a relay(that's the most ''compressed" explanation i can give)

sierrafery said:

The wiring from the sensor doesnt go directly to the ECU it passes through connector C0391/0377 which is in the engine bay but that might not be relevant for the fault i mentioned it only for accuracy ...

did you completely remove the old wires at the ECU plug and pinned in the new ones? .... if yes the ECU is very suspect, the fault code is about the ECU's 5V supply to the sensor cos that "power amp." is an electronic switching circuit within the ECU which acts as a relay(that's the most ''compressed" explanation i can give)

Click to expand...

Ah that does make a little more sense. I figured there’d be a connector somewhere along the pipeline but couldn’t see it on any of the (simplified) diagrams I came across!

The direct wire seems to have worked well in terms of stabilising the height sensor readings (before re wiring it was ranging from 2-200 and anywhere in between continuously)

You make a good point re. new pins. As I was mainly testing the new cable for wether or not it would work at all I cut the body wires from the ECU plug pins 123 and left short tails and crimped the new cable to those. Will that extra resistance be enough to cause a problem? It keeps coming back to me that this fault was present before modifying any wiring so maybe it is the slabs ECU itself. I have a spare but it is a different p/no?

Edit : thank you thank you thank you!!

Welcome.

You can swap the ECU cos it will work regardless of the part number, you just have to set it for SLS and calibrate heights eventually... the difference between ECUs is in the ABS system's behaviour while the central diff is locked, the SLS side is the same in all... better rule this out before working more on wirings

edit, dont remove the old ECU at first cos it's a nightmare, just unplug it and plug in the replacement for test before you become a contorsionist

sierrafery said:

Welcome.

You can swap the ECU cos it will work regardless of the part number, you just have to set it for SLS and calibrate heights eventually... the difference between ECUs is in the ABS system's behaviour while the central diff is locked, the SLS side is the same in all... better rule this out before working more on wirings

edit, dont remove the old ECU at first cos it's a nightmare, just unplug it and plug in the replacement for test before you become a contorsionist

Click to expand...

Right then, swapped to the spare ecu, I still get the fault but not nearly as much, I can drive for an hour or more and it won’t come on yet suddenly it bongs up, key off and back on and fault gone until next time!

So I don’t think it’s ECU based really as the fault is still present although doesn’t seem to occur so often - maybe going to switch back to original ecu and see what it is like.

I guess it’s a wiring issue somewhere/somehow. Possibly the use of crimped connectors over direct join to a new pin or a soldered joint?

Or the new sensor is playing up, swap the sensors between them and see if the fault stays on the same side

Back at it! Disco still beeping it’s head off!!

Another brand new sensor and no difference.

Soldered the connections of the new wire as opposed to using bullet connectors I’d used initially.

Still no difference, one thing I do notice is the constant beeping stops on a long right hand bend when the car leans left - I wonder why! As soon as the car straightens up it starts again

Feel like burning the thing right now

One thing I thought - what if I have managed to get the supply/signal wires the wrong way around but I don’t think so as I get steady height readings now.

And what's the fault code now?

sierrafery said:

And what's the fault code now?

Click to expand...

Same code as before, LH power amp short to ground

Confirm again two things:
1. did you wire the sensor directly to the ECU plug and replaced the sensor side connector too?
2. the fault code was the same with the spare ECU too

1. Yes brand new height sensor connector and wire wired directly into the 3 left hand sensor input wires about an inch before the ecu C0654 plug.

2. Same fault code, although the original ECU seems far more sensitive to this problem than the other different p/no spare I tried - ie. it faults much sooner into a drive.

You'll have to make continuity tests between the ECU plug and sensor plug to see if you didn't accidentally mix the supply with the return wires at the sensor so pin 1 ECU - to 5 sensor, 2 to 1 and 3 to 4....If the circuit is good the only place left for that short is connector 0654

sierrafery said:

You'll have to make continuity tests between the ECU plug and sensor plug to see if you didn't accidentally mix the supply with the return wires at the sensor so pin 1 ECU - to 5 sensor, 2 to 1 and 3 to 4....If the circuit is good the only place left for that short is connector 0654

Click to expand...

Hey,

Continuity perfect on all 3!

I have however reconnected the spare SLABS ecu and driven around 5 miles with no faulting - I will keep an eye on it over th coming days

I’m wondering if one of the crimped connections was a little loose which I have resolved by doing a soldered joint and the car’s original SLABS ecu is poorly.

Time will tell, thank you again for your help

Yes, well done cos the ECU was suspect from the beginning, fingers crossed

It’s back

Make another test, erase the code then while it's on even level set the system to coils and drive it so for a while see what happens then read codes again ... and please tell again the exact description of the fault code you are getting code(go to the next page too on hawkeye as to not miss anything)

Hey,

I had it set to coils last week for a few days of peace from the beeping. It registers no fault codes whilst in coil configuration at all.

I will do so again tonight
Photo above is the exact fault. It becomes historical as soon as ignition is switched off.