L322 Engine failsafe - Car left me stranded

Nightmare of a day today. I swear I spend more time fixing this car than using it.
2003 l322 vogue petrol

Heavy rain on the motorway a couple of weeks ago. Air susp inactive message came up. Ordered all comms and carried on using it. After another week hdc inactive came up as well. Abs and tractions control lights on and brakes started coming on automatically (like hdc) when performing slow manuvers such as driving in/out of my driveway. Visual inspection showed height position sensor had become detached from suspension arm. Ziptied back on as a temp fix, all comms arrived, cleared faults, suspension back working again (compressor running ok etc) but after 2 mins driving the hdc inactive came back. Checked codes again and front left speed sensor implausibility shows. This is strange as it is opposite side to the height sensor that I had an issue with.

Today I raised the suspension, had a look around both front wheels and checked all wiring in those areas to see if any corrosion /loose connections etc. All wires don't look the best but nothing obvious noted. I also topped up brake fluid level as I noticed it was a bit low (i must have a slow leak of some sort as this is the second time in the last six months doing this). Cleared faults and tried again. Car didn't start very well and immediately started misfiring. Engine failsafe prog shows up on dash. This actually happened briefly a few weeks ago after another strange start to the car. I turned off then and restarted and it has been fine). I did this again and car started ok and no faults. Read faults with allcomms and suspension shows CANbus fault. First time seeing this. Cleared faults and took car for a drive. Hdc inactive still there but worked ok. Drove the car later to pick up a takeaway for tonight and it was fine on the way there. Started car to drive home and has the same issue as earlier. Engine failsafe prog, car misfiring like crazy and accelerator does nothing. Checked codes again, only can bus fault on air suspension. This refuses to clear. No other codes. Tried basic stuff like disconnecting battery and doing a full reset, steering lock to steering lock in case it needed calibrating (this makes a horrible clicking noise and even stalled the car on full lock) also tried accelerator calibration but turning to pos 1 on ignition and depressing fully before turning back off. Nothing else shows on all comms and car still immediately goes into limp mode when it starts.

I ended up having to limp to car home, hazards flashing and misfiring and auto braking all the way home. Accelerator still does nothing so it was chugging along at 2mph.

Does anyone have any idea what I can do? Allcomms is giving me no clue and I am stumped to what to do. I'd appreciate any advice! Thanks.

1st port of call is the battery good ?
2nd port of call ant the saint will be along soon hes had practice with canbus probs

Thanks for the remind Wil....

What faults are showing in the M62 Engine Logs (if any?)

Most common Eng Failsafe issues are to do with what BMW call the EDK which is the Electronic Throttle Body.....

The DME7.2 (Bosch Digital Motor Electronics) uses a fly-by-wire throttle system....the pedal (called the PWG) has two pots in it, these provide pedal position information to the DME, the DME then measures this and applies it to various different throttle control maps based on current driving conditions etc and then motors the EDK motor to open the throttle butterfly to provide the necessary change in engine speed and power output.....

The DME also uses information from the ABS/DSC unit via the CanBUS as is the DSC requires throttle reduction to maintain control, it requests this from the DME and the DME then closes the EDK slightly to reduce engine output.....

It might be one of a few things.....

The ABS/DSC is giving spurious info to the DME asking for power reduction - this shouldn't bring on the Eng Failsafe
The EDK is failing to provide feedback to the DME on throttle butterfly position - this will bring up the Eng Failsafe - but is more common on the BMW M72 V12 in the E38...but not unheard of on the M62
Fuel pressure reduction caused by clogged filter - shouldn't cause Eng Failsafe, but if misfires are that bad, it will shut the engine down and put on Failsafe


I would be inclined to take a closer look at the ABS sensors first, the front wiring does have a tendency to rub on the inside of the wheel rim and wear out.

Pull engine codes and report back.

Bedtime reading attached..... http://e38.org/m62tu.pdf

Thanks both, the help is really appreciated.

I've spent a few hours fault finding but my working hours and the winter daylight time is proving a challenge to get the wheels off and have a look at the abs sensor. After further reading, I found that if I start the car with the MAF unplugged she starts fine. I then plug it back in and the car runs great as it did before. I did this this morning on the way to work and stopped at a petrol station. When restarting with the MAF plugged in it worked fine again without a failsafe, but then after pulling up outside work 50 miles later, I turned it off and on and it went back into failsafe until I pull the MAF again. It seems the self check it does prior to starting is causing the eng failsafe mode to kick in. The codes on the M62 are thottle adaptation spring test failed. Reading up on this it looks like the throttle body pots might be going bad (or have been for a long time) and the MAF maps have adjusted to deal with it. When I plugged my allcomms in for the first time, it's cleared the MAF's maps and therefore has to perform a relearn and it doesn't like the degrading TB pots and puts it into safe mode. Unplugging the MAF when starting, skips this relearn and therefore it's fine after. I hoped the long drive today would give a chance for the MAF's to set new maps without tripping the failsafe and then it would be fine again, but sadly it seems not.

I am unsure if this is the problem or is it related to the wheel speed sensors as you suggest. I guess it'll have to wait until the weekend now when I get a chance to see if there's a problem there. Grateful for any further advice given the info above.

thanks again

Just managed to crawl under the car and check the speed sensor. It looks fine with no damage to the cable or anything loose. Code shows front left speed sensor plausibilty. I reset the codes anyway and tried again but the same thing happens, Engine failsafe, hdc inactive, loads of lights on dash. The same code popped up again as well as throttle accuator spring test failed also.

Think you are narrowing it down.....sounds like the throttle body is losing its head!

Saint.V8 said:

Think you are narrowing it down.....sounds like the throttle body is losing its head!

Click to expand...

Thanks Saint but I wish I could be as optimistic as you! Do you know if the allcomms has the ability to clear maf maps or clear ecu self learn and the like? If not are there any other tricks I can try?
Also when abs sensors start throwing codes and the wiring seems fine, is there any other likely culprits? I dread just having to change it as its most likely corroded to the hub. Thanks again

The ABS 'Short' harness to the ABS ECU under the bonnet has been known to suffer water ingress...LR released a Tech Bulletin about it which was to splice in a new short harness (I have done this when I had odd ABS faults - didn't solve mine, more below). Pull the ABS ECU plug off and check for any signs of corrosion on the plug and pins.

The ABS ECU due to its location above the exhaust manifold and with no heat shield, they do tend to suffer ECU failures....basically there are tiny little wire connections inside the ECU and the joints go dry and crack from all the thermal expansion and contraction due to the location.....this is what happened to mine, replaced the ECU and all was well. I did a thread on the Harness replacement and also the ABS ECU issue too....a search should throw something up!

Now, neither of these should give ENGINE FAILSAFE warnings....this warning is usually reserved when the DME can't determine the correct engine parameters, chiefly throttle position, and shuts the engine down to limp mode or off altogether for safety.

The fact you are getting throttle plausibility codes could indicate either Throttle Body or Pedal Potentiometer issues.

I am not sure if the All Comms resets fuel trims when you clear codes....I assume it does!

You can get cheap ELM327 OBDII cables from Amazon, and there is also a free software called EasyOBD that will read codes and also will reset the fueling adaptions/trims as it warns you it will reset the trims to zero when you hit 'Clear Codes'.

Using the ELM327 and EasyOBD, you can get live data from the MAF and the Lambdas, Coolant Temps, intake air temps etc.....so if you suspect the MAF, this will give you metered air quantity readings that can be compared to others data to qualify your MAF is or isn't working correctly.

Final thing to try would be another Throttle Body....it is from memory only 4 bolts (Torx bit I think) and the intake ducting, remove the multiplug and its off.....not sure if the Body will need pairing or coding to the vehicle, you'd have to research that first obviously...I assume the DME needs to know the butterfly open and closed set points ... but this could also be self-learnt by the DME....not sure...will have to check.

just to throw another possibility into the pot as i had engine failsafe issues last year, no misfiring but engine going into limp mode within seconds of firing up, it turned out mine was the engine ECU went faulty, mine was shorting between the thermostat heater circuit and throttle body circuit causing issues, the whole fault was started by the ebox fan partially seizing and not providing enough cooling for the ecu.

Water tracking up the loom into the ECU are common on the L322.....as you say it tracks up from the thermostat heater connection!

Thanks both, I'm going to dedicate this weekend to solving it. I'm suspecting its two separate issues. One with the abs and the other with the throttle body. I'm guessing the abs is something loose as it first came on after going over a bump in the road and then disappeared for a few days before coming back again and staying on. Please keep me in your prayers haha. Thanks guys.

it took me weeks to find my ecu fault because with the car cold it wasn't there, i tried replacement throttle body/ pedal etc and still couldn't clear it, then one day a checked the wires with a multi meter when the car was warm and found it, initially i thought it was a short in the wiring until i unplugged the ECU and the fault went. mine was however the ECU went faulty and not from water tracking up through the wires. if you do need an ECU i can put you in touch with the guy that reprogrammed a used ECU for me it cost me £150 for the ecu and £120 for the reprogram. far cheaper than the £800 quoted by LR for a new ecu

Going over bumps can still put the ABS ECU into fault as the bumps dislodge the tiny wires inside. Search my threads for it, also google it as it is quite common on the BMW cars with the same system....chiefly the E39 5'er.

A hairdryer can prove to be an excellent 'tool' for troubleshooting suspected thermal gradient/expansion issues, (especially with electronic modules), but it is not always practical - unfortunately.

Any module that produces heat, (power semiconductors in the BCU is a good example), will slowly change the molecular structure of their own soldered joints and this can then spread to other adjacent solder joints close by resulting in 'dry joints' which are very common in high power circuits.

Add vehicular motion, (vibration), and the process is accelerated and if you then add water ingress to the mix you have the initialisation of a wide range of auto electrical problems that will then prove to be intermittent, illogical and highly frustrating but rarely expensive to fix if correctly diagnosed.

Ironically all of my current problems appear to be mechanical, (primarily bodywork related - not one of my better skills), but whenever I am presented with a suspected module issue I will firstly try and replicate the problem, (under static conditions - if possible), by use of: -

1/. 'Measured' tapping of the module and/or circuit board whilst monitoring a suitable output, (be it a measured voltage or simply listening for a subtle change in the engine tone), in order to highlight mechanical issues, (poor solder joints or corrosion within connectors).

2/. Carefully applying heat to the area of interest, (in a controlled fashion), in order to test for thermal expansion issues, (that are perfectly stable when the module is cold) - but which introduce high resistance once the molecules start to become agitated as the temperature rises whilst, once again, monitoring a suitable output for any audible/visual changes.

The reliance upon a multitude of sensors, (ride height, abs wheel speed, throttle position, knock, etc), add an additional level of 'mechanical' vulnerability to the systems under examination which can also result in some very unusual, unpredictable results - all of which highlight the benefit of enthusiast forums, (such as this one), as there are some very knowledgeable members around who have been through the 'pain' barrier and learned from experience and can then identify the root cause of those bizarre Range Rover traits - my journey has just begun!

All absolutely useless when trying to repair my boot floor of course - although, ironically, ALL electronic component failures are ultimately due to mechanical breakdown/failure - but on a slightly smaller scale than my bodywork!

Good look - maintain a logical approach and you will nail it!