Driving home from Cardiff last night quite happily around the M42 and without warning the car made a clunk and EVERYTHING shut down. Christmas tree lights on the dash then battery light. No 'power' steering or brakes as such but the gearbox went into neutral (I think anyway as I coasted across lanes to the hard shoulder and was eventually recovered by the RAC.Threw a few codes but the relevant ones were P0A1A 87 and B1087 93 which appear to point to a 'Generator Control Module' that I can find NO information about? Alternator yes...BMS...yes, Sensor wire from alternator I have found but no GCM? Any clues? If there is already a thread here I apologise and would appreciate some guidance.
P0A1A 87 code
- Thread starter Schildy
- Start date
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2012 MY L320 TDV6. No warning and complete shutdown. At this moment I have nothing to go on apart from checking alternator sensor wire and that's about it? So you say 400a fuse...I'm assuming 'mega fuse' on the positive battery side?
Yep, that's the one - will the engine crank?
Those DTC's are generally consequential rather than causal when you get them together.
Addendum - the 'generator control module' is what would traditionally be called the regulator component of the alternator, the 'sensor wire' is actually a LIN communication line between the PCM & the alternator, the GCM gets its power from the +ve connection to the battery (via the mega-fuse) so loss of power on that connection will mean the GCM cannot be communicated with, hence the DTC.
If the engine won't crank and the fuse is OK, check the engine earth strap or put a jump lead between the battery -ve and a suitably heavy & clean bit of the engine and try again.
Those DTC's are generally consequential rather than causal when you get them together.
Addendum - the 'generator control module' is what would traditionally be called the regulator component of the alternator, the 'sensor wire' is actually a LIN communication line between the PCM & the alternator, the GCM gets its power from the +ve connection to the battery (via the mega-fuse) so loss of power on that connection will mean the GCM cannot be communicated with, hence the DTC.
If the engine won't crank and the fuse is OK, check the engine earth strap or put a jump lead between the battery -ve and a suitably heavy & clean bit of the engine and try again.
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REALLY appreciate your feedback. Engine won't crank full stop but when 'pushing the button' you can hear the solenoid click? I'll pick this back up tomorrow as it's tipping down and I'm already fed up enough not too get soaked in the process. But it sounds as if the alternator had a 'fatal'?
If the solenoid is clicking, then most likely the starter is OK, as is the engine earth.
I take it there's no dimming of interior lights or dash going off when you attempt to crank the engine?
Next step is to check the Mega-fuse, easy enough with a volt meter or even a test light, but yes, without further confirmatory checks, the alternator is the likely cause.
I take it there's no dimming of interior lights or dash going off when you attempt to crank the engine?
Next step is to check the Mega-fuse, easy enough with a volt meter or even a test light, but yes, without further confirmatory checks, the alternator is the likely cause.
You don't need the ignition on, identify the fuse block on the battery +ve terminal, there are two red cables coming from it, one goes to the battery junction box next to the battery, the other thicker one comes out of the side of the battery enclosure and down to the starter & alternator. This is the one you need to check for 12V at. you can either probe up the side of the cable where it enters the black enclosure around the fuse, or remove the cover which is clipped on, and test directly between battery -ve and the bottom connection of the fuse and the heavy cable. It'd probably be easier to temporarily disconnect the battery terminal to remove the cover.
And if all measures ok through the mega you would suggest the likely problem WOULD be the alternator? When ‘attempting’ to start no drop in brightness of interior lights or dash that I can see. The ONLY tell tale is that solenoid click. Would that sudden shutdown (there really was no warning) be a causal of the alternator having a total immediate failure? It’s going to have to go to a local garage for repair either way as I have no way of doing this where I live but understanding your replies helps me describe when I get there.
If the fuse is OK, then it's either a poor engine earth - but I'd expect a lot of other DTC's or odd behaviour, or a wiring fault.
If the fuse is intact and you press the start button, with a faulty starter motor, you'd see some dimming of the interior lights and flickering of the dash lights etc. Besides, the starter motor is electrically isolated when not cranking so that wouldn't cause the fuse to rupture during driving. The alternator is of course, connected to the battery whilst driving, assuming an internal defect in the rectifier pack or windings caused a short to ground, that would initially draw lots of current from the battery in a short time until the fuse ruptures (the fuse may well have ruptured after the vehicle came to a halt).
All of the above assumes that the mega-fuse has blown due to an alternator fault and not due to previous attempts to start the engine after it stopped (which you didn't mention so I'm assuming there were none) and the fuse has blown due to a seized engine causing excessive current to be drawn by the starter motor - which would give the same DTC's once communication with the alternator was lost. The basic check for this is to rotate the crank pulley in a clockwise direction only, if you get 'soft' resistance, rest for a few seconds and go again, aiming for two complete revolutions (put a Tippex or crayon mark on the pulley first). If you get 'hard' resistance (sudden stop, not gradually increasing), then it's likely to have suffered a catastrophic failure internally.
If the fuse is intact and you press the start button, with a faulty starter motor, you'd see some dimming of the interior lights and flickering of the dash lights etc. Besides, the starter motor is electrically isolated when not cranking so that wouldn't cause the fuse to rupture during driving. The alternator is of course, connected to the battery whilst driving, assuming an internal defect in the rectifier pack or windings caused a short to ground, that would initially draw lots of current from the battery in a short time until the fuse ruptures (the fuse may well have ruptured after the vehicle came to a halt).
All of the above assumes that the mega-fuse has blown due to an alternator fault and not due to previous attempts to start the engine after it stopped (which you didn't mention so I'm assuming there were none) and the fuse has blown due to a seized engine causing excessive current to be drawn by the starter motor - which would give the same DTC's once communication with the alternator was lost. The basic check for this is to rotate the crank pulley in a clockwise direction only, if you get 'soft' resistance, rest for a few seconds and go again, aiming for two complete revolutions (put a Tippex or crayon mark on the pulley first). If you get 'hard' resistance (sudden stop, not gradually increasing), then it's likely to have suffered a catastrophic failure internally.
A seized engine? Now you are scaring me? It coasted to a controlled stop albeit I had no power steering or 'soft' brakes, I had to stand on them to stop. But I assumed this was because the car lost electrical and shut down' now you are saying seized engine. Would there not have been a 'bag of bolts' scenario if that had taken place? I'll have to try the crank scenario and take a look tomorrow now.
It's a possibility - an auto will 'coast in' once the torque converter unlocks (which will hopefully have been the 'clunk' you mentioned), generally with internal engine failures, there's a loss of power or unusual noise - sometimes briefly, before the engine stops. Clearly not something you'd want to hear, but it's possible.
I experienced something similar a few years ago which resulted in requiring a replacement TDV6 engine, the cause was a failed fuel injector which cut a hole in the crown of a piston, in turn allowing the engine oil to be ingested and burnt. All was well until climbing up the hill approaching J6(?) on the M40 on cruise control, instead of going up at the speed set, the car was slowing, dropping a gear caused lots of engine vibration, stopping at the top of the junction revealed the smell of 'dead fox', which is what engines with no lubricant in them smell like...
I experienced something similar a few years ago which resulted in requiring a replacement TDV6 engine, the cause was a failed fuel injector which cut a hole in the crown of a piston, in turn allowing the engine oil to be ingested and burnt. All was well until climbing up the hill approaching J6(?) on the M40 on cruise control, instead of going up at the speed set, the car was slowing, dropping a gear caused lots of engine vibration, stopping at the top of the junction revealed the smell of 'dead fox', which is what engines with no lubricant in them smell like...
From what 'sufferers' have told me, it generally seems to feel like a sudden, brief headwind, dabbing the brake pedal or pulling the handbrake on older cars. Without 'being there' I can't really say it's better than a 50% chance at this stage, better to mention it than not IMO.
Did you make any/many attempts to restart the engine at the time of breakdown? did the lights dim excessively when you did?
Did you make any/many attempts to restart the engine at the time of breakdown? did the lights dim excessively when you did?
I will definitely be trying the crank turn tomorrow…great way to spend the New Year but at least I’ll not have a hangover
There were other DTC’s but I associated these to the fact they were transmission/gearbox related after the recovery guy had used the ‘emergency’ gear puller under the console to get it into neutral? 2x TCM 1x GCM and 1x RFA
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