engine failsafe mode

hi guys first post here, hopefully someone can help me get to the bottom of this issue, i have posted this also on another range rover forum and so far no one has had any ideas. after a week of trawling the internet and various tests i'm still getting engine failsafe mode followed a few seconds later by hdc/air suspension inactive, brake warning light, abs warning light and occasionally the engine check light, also accompanied by error code po120 & po221 (throttle potenometer 1 &2) and occasionally throttle stop lower learn, i clear these codes and they come back within seconds even if the car is not running. it's a 2003 l322 with bmw m62 4.4 v8 engine, issues exsist on petrol & lpg, so far i ahve done the following:

changed accelerator pedal (twice) both used units but rule of thumb both shouldn't be faulty
checked all the wires from throttle body to ecu every one has .1 ohm resistance
checked thermostat this has proved to be ok with no sign of overheating on the plug
tried a different throttle body today but as this is a used unit from a breaker probably untested so could be faulty
checked the blue ground wire from the throttle body to earth through the ecu, .1 ohm resisitance
checked battery after car been stood for 8 hours it's showing 12.5v
checked the alternator, my local alternator centre say it's ok, it's pushing out 14-14.1v at tickover and i don't see the battery light come on with everything running, i retested it today headlights on main beam, air con on, heater blower full and it was showing just over 16 volts, but went back to 14 once everything was off.
this morning checked wires to accelerator pedal with multi meter i have 5v in on 2 pins, ground on 2 pins meaning the other 2 pins must be signal back to ecu

if i press the accelerator pedal there is a slight hesitation before the car revs, followed by a drop in revs before it picks up and ticks over normally. but throttle body opens and closes normally with pedal movement.

hdc/ air susp inactive etc usually trigger after engine failsafe and i hit approx 30mph

i checked the actuators operation at tick over with hawkeye and idle valve/ actuator shows active for a second then switches to inactive not sure if this is correct?
i have also noticed a couple of times when it triggers with ignition on but engine not running, it trys to close the throttle butterfly a little further than it is sitting normally, then just releases it, not sure if this is normal.

apart from this issue car drives normally and is not down on power i don't want to buy a throttle body if it's not the issue, especially at £316 plus vat, although bmw have just quoted me £204 plus vat

most of the bmw sites report loss of power with engine failsafe mode i'm not experiancing any loss of power

live data taken with hawkeye
error codes p0120 & p0221
Throttle potentiometer 2
Throttle potentionometer


Live data
Eng speed fluctuates from 576-630
Eng spec speed 600
Coolant temp 95c
Rad cool temp 52c
Intake air temp 43c
Air mass 18.9-19.2 kg/h
Timing 189.5 kW
Inj time 3.8 ms
Throttle pos 1%
Battery 13.8 volts
Throttle pot1 .59v. Ful throttle 4.36
Throttle pot2 1.53v full throttle .37 volt
Pedal trav sens 1 .33v full throttle 2.31v
Pedal trav sens 2 .65v full throttle 4.66v

Engine Failsafe usually means the ECU/DME can't correctly determine Engine sensor parameters or throttle pedal position or throttle butterfly position and as such instead of letting the engine run away with itself (as the DME isn't sure if the throttle is stuck fully open which would be very dangerous for the engine) so it cuts fuelling to stop or slow the engine.

Battery voltage should never be in excess of 14.8 volts while running...16V is way to excessive and can lead to electrical component failure. Maybe this could be the problem.

The throttle bodies are extremely reliable so very much doubt it is that....

BUT one of the biggest and common issues on the M62 engine is the Electrically controlled Thermostat leaks and the coolant tracks up the wiring loom and corrodes the connections to the Engine ECU .... this *may* be your issue!

Take a goosey at Timm's BMW M62TUB V8 Engines - Engine Failsafe and also www.meeknet.co.uk/E38/m62tu.pdf as this gives a bit of background information on the engine sensors and systems.

Might be time to take it to a dealer with the Testbook T4 system as with this they can use it to run scope tests on sensor outputs and compare to book data.

As Saint said, you should never see 16 volts from the alternator, could be there are transients much higher than that likely to cause damage to the electronics.

thanks for the info guys, i've checked the thermostat and there are no signs of the plug overheating or any sign of the thermostat leaking, i have also checked the ecu whilt i was checking ecu to throttle wiring and no signs of water damage on that end, when i checked the alternator yesterday i never noticed the battry was low in my multimeter so could explain the voltage reading, i have checked it again today in the same situation (new battery in meter) and getting 13.9/14v with mainbeam/heater blower on and the same with everything off and just on tickover. still trwling the net and throttle pedal keeps coming up connected to the error codes. but both replacements faulty would be really bad luck. i am contemplating just replacing the pedal but hesitant as i think there maybe something else possibly causing this

RRkev said:

thanks for the info guys, i've checked the thermostat and there are no signs of the plug overheating or any sign of the thermostat leaking, i have also checked the ecu whilt i was checking ecu to throttle wiring and no signs of water damage on that end, when i checked the alternator yesterday i never noticed the battry was low in my multimeter so could explain the voltage reading, i have checked it again today in the same situation (new battery in meter) and getting 13.9/14v with mainbeam/heater blower on and the same with everything off and just on tickover. still trwling the net and throttle pedal keeps coming up connected to the error codes. but both replacements faulty would be really bad luck. i am contemplating just replacing the pedal but hesitant as i think there maybe something else possibly causing this

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Maybe your meter s NBG, but you should have a minimum of 14.2 volts and more like 14.5 volts from the alternator.

Datatek said:

Maybe your meter s NBG, but you should have a minimum of 14.2 volts and more like 14.5 volts from the alternator.

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hi datatek that's exactly what i thought to be honest, but after getting it checked my local alternator centre said 14.1 was fine and the same on another range rover site, i'm now thinking possibly alternator starting to fail, i've contacted my local stratstone to get the car in for diagnostic check, just waiting for them to call back. my initial worry is the engine failsafe mode and throwing up code p0120 & p0221, which even with a battery charger on the car earlier and the engine not running it still threw up the codes, the battery is only a year old and a bosch unit.

RRkev said:

hi datatek that's exactly what i thought to be honest, but after getting it checked my local alternator centre said 14.1 was fine and the same on another range rover site, i'm now thinking possibly alternator starting to fail, i've contacted my local stratstone to get the car in for diagnostic check, just waiting for them to call back. my initial worry is the engine failsafe mode and throwing up code p0120 & p0221, which even with a battery charger on the car earlier and the engine not running it still threw up the codes, the battery is only a year old and a bosch unit.

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Just because the battery is branded Bosch and a year old does not mean it's any good, battery failure in new batteries is common these days.
Alternator need a scope on it to see if the output is pulsing.

cheers datatek, on test i have found the battery to hold 12.5 volts after the car being stood for 8 hours, that's after a run with headlight etc on, i think i may keep a check on the live data with hawkeye on my run to work tonight, unfortunately it only measures battery voltage not alternator output, but it usually measures the voltage at around 13.8 volts

RRkev said:

cheers datatek, on test i have found the battery to hold 12.5 volts after the car being stood for 8 hours, that's after a run with headlight etc on, i think i may keep a check on the live data with hawkeye on my run to work tonight, unfortunately it only measures battery voltage not alternator output, but it usually measures the voltage at around 13.8 volts

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Not sure on yours, but on the P38 there is quite a voltage drop between the battery and the OBD port. If 13.8 is the actual battery voltage it's too low. If the battery is holding 12.5 volts it may be OK but would need a shunt test to be sure.

12.5 volts at the battery is low. My L322 starts to misbehave at 12.7V
I can't say if that's your root cause but it's going to make any further diagnostics difficult.

H

Oops. Meant to say.
Have you got access to a known good battery?

Datatek said:

Not sure on yours, but on the P38 there is quite a voltage drop between the battery and the OBD port. If 13.8 is the actual battery voltage it's too low. If the battery is holding 12.5 volts it may be OK but would need a shunt test to be sure.

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yes there could be on the l322 as well, during a test earlier alternator was charging at 14v and haweye was showing 13.87 on live data, but at least if i have it sat in front of me it should show any pulses/spikes and i can double check that voltage does not go to high again

RRkev said:

yes there could be on the l322 as well, during a test earlier alternator was charging at 14v and haweye was showing 13.87 on live data, but at least if i have it sat in front of me it should show any pulses/spikes and i can double check that voltage does not go to high again

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The Hawkeye is not fast enough to show spikes or any AC component that may be there.

Herald said:

Oops. Meant to say.
Have you got access to a known good battery?

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i don't have access to anything the size of the range rover, my other car's battery is half the size

Just driven 20 miles to work with hawkeye tracking battery info, it started off at 13.77-13.94 volts, after about 15mins this reduced to 13.58-13.68 volts lowest it went was 13.49 a couple of times, this was with air con running. I did notice throttle position at tick over never went below 2%, although when I was sat in traffic towards the end of my journey it was sitting between 1% upto 4%

RRkev said:

Just driven 20 miles to work with hawkeye tracking battery info, it started off at 13.77-13.94 volts, after about 15mins this reduced to 13.58-13.68 volts lowest it went was 13.49 a couple of times, this was with air con running. I did notice throttle position at tick over never went below 2%, although when I was sat in traffic towards the end of my journey it was sitting between 1% upto 4%

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What Hawkeye is reading is the voltage as read by the instrument pack...this voltage will always be slightly lower than Alternator output!

datatek said:

just because the battery is branded bosch and a year old does not mean it's any good, battery failure in new batteries is common these days.
Alternator need a scope on it to see if the output is pulsing.

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+1

i've now got the car booked in with my local land rover indy next week, they think it maybe possibly to do with adaptive settings on the ecu, but they are running full diagnostic, clearing all adaptive settings then i take car for a drive for 10-15 mins then they will rescan to see which codes if any have come back.

RRkev said:

i've now got the car booked in with my local land rover indy next week, they think it maybe possibly to do with adaptive settings on the ecu, but they are running full diagnostic, clearing all adaptive settings then i take car for a drive for 10-15 mins then they will rescan to see which codes if any have come back.

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Generally fuel trim adaptions reaching their limits won't cause Engine Failsafe, it will bring on the EML and log faults, but unless something is seriously out of whack, Fuel Trims shouldn't cause it....reset them and see what happens as I would be intrigued to know.

I have at home a document on Fuel Trims and how they work and effect the running of the engine based on the DME of the E39 5'er BMW which uses the same the same engine and DME system as the L322 (and also the E31 8'er, the E38 7'er and the E53 X5)...might be something in there, I'll see if I can dig it out for you!

brilliant thanks saintv8, they did also say on the phone it 'could' be a issue with the lpg conversion wiring, but that's been on the car since 2009 and regularly checked & serviced, only thing i've picked up on looking through tech documents is throttle pots one starts at .5 volts and goes upto 4.5v the other works in reverse 4.5 down to .5 but mine is out on live data with pot1 one ranging from .59v to 4.36v and pot 2 starting at 1.53v dropping to .37v so something not quite right there, the wiring plug to the throttle has been noted as causing errors from bad connection, but so far i've been unable to track down a new one, it's worth a try. i also had a problem with the ebox fan being partially seized and not cooling propperly so hopefully the ecu hasn't got to hot and gone faulty.