Hi Folks,
I'm hoping someone might have some thoughts on this strange situation. I recently completed an engine rebuild on my 2003 C2 3.6 whose LN ceramic bearing failed after only 65,000km. The rebuild took two years end to end as I had to shelve it for periods due to life's other challenges. It fired up almost a month ago and all was well with about half an hour of test drives around my "private test track" and 10km run into town for the equivalent of your MOT. So far it had behaved perfectly. But during the short test drive for registration (MOT equiv.), it stalled on the inspector and would not restart. Of course I nearly died fearing an engine problem but no all was well, we had all lights and electrics working but no crank. After maybe 15 mins checking fuses etc it cranked and started perfectly, but then stalled at idle again after 30seconds or so and I had it tilt trayed home.
The no-crank fault seems intermittent but getting worse, the last few days it has been all 'no crank'. At first it would occasionally start and run a short time, but most often it has the 'no crank' behavior exactly as per using my old un-coded key. Every single other electrical device works perfectly even when it is in the 'no crank' mode - including the central locking remote! I only have a Foxwell scannner, but it will connect to all modules including the alarm, there are no faults* in any module, and when using either of my 'good' keys (both new genuine ones 2 years ago) the immobiliser status goes to 'Active' for about a minute after ignition-on, then changes to 'not active'. If I use the old key it is always 'not active'.
So from this it seems the pill in the key is being read ok, and decoded and matched ok. Due to the behaviour of the old key I take 'active' to mean the engine should be active, rather than the immobiliser being active (ie preventing start). So at the software level the alarm module seems to be happy but maybe something goes awry on the output stage of the board?
Thus far I have done the following;
Does anyone have any ideas of where a problem might arise other than the modules? Another relay somewhere? Are there any other tests I can run before pulling out the modules and sending them away? At least there does appear to be an Australian company (Injectronics) who advertises testing/repair, although there are a disturbing number of recent one-star reviews on google. The thought of having to replace the DME/Alarm/Keys at dealer prices terrifies me!
Sorry for the long winded post, appreciation if you've made it this far...
Steve
I'm hoping someone might have some thoughts on this strange situation. I recently completed an engine rebuild on my 2003 C2 3.6 whose LN ceramic bearing failed after only 65,000km. The rebuild took two years end to end as I had to shelve it for periods due to life's other challenges. It fired up almost a month ago and all was well with about half an hour of test drives around my "private test track" and 10km run into town for the equivalent of your MOT. So far it had behaved perfectly. But during the short test drive for registration (MOT equiv.), it stalled on the inspector and would not restart. Of course I nearly died fearing an engine problem but no all was well, we had all lights and electrics working but no crank. After maybe 15 mins checking fuses etc it cranked and started perfectly, but then stalled at idle again after 30seconds or so and I had it tilt trayed home.
The no-crank fault seems intermittent but getting worse, the last few days it has been all 'no crank'. At first it would occasionally start and run a short time, but most often it has the 'no crank' behavior exactly as per using my old un-coded key. Every single other electrical device works perfectly even when it is in the 'no crank' mode - including the central locking remote! I only have a Foxwell scannner, but it will connect to all modules including the alarm, there are no faults* in any module, and when using either of my 'good' keys (both new genuine ones 2 years ago) the immobiliser status goes to 'Active' for about a minute after ignition-on, then changes to 'not active'. If I use the old key it is always 'not active'.
So from this it seems the pill in the key is being read ok, and decoded and matched ok. Due to the behaviour of the old key I take 'active' to mean the engine should be active, rather than the immobiliser being active (ie preventing start). So at the software level the alarm module seems to be happy but maybe something goes awry on the output stage of the board?
Thus far I have done the following;
- Battery tested and confirmed OK, also swapped another battery, no change.
- Check main electrical connections like battery- to body, body to engine, disconnect/reconnect both plugs in the engine bay, check main +ve lead to engine bay, and Y-cable to starter/alternator. This car has lived since 40,000km and 2009 in a dry part of Australia away from the coast and has zero corrosion anywhere. I inspected the fabled Y-cable during the rebuild and concluded it was fine.
- Ignition switch replaced with new genuine unit, no change.
- At one point it started and ran poorly and threw a bunch of codes that lead back to MAF. Last thing I did in the rebuild was clean and oil my BMF air filter. I swapped back to the original airbox/paper filter and cleaned the MAF with magic spray. Now it just threw an actual DME MAF error. Strangely, at that time regularly cranking fine. Got a new MAF (genuine Bosch) but since installation it has not cranked. I think MAF problems were a secondary issue from over-oiling the filter and were not related to the original stall/no crank issue.
- Now I actually started to diagnose rather than swap parts. I found a wiring diagram and traced back from the starter to the "Start Lock Relay" in the rear DME/relay area. The area is pristine, looks ex-factory. I had 12v on pin 86 (coil +ve) with ignition on, and 12v on pin 30 (contact input) with key in start position. I jumpered from pin 30 to 87 (contact input to output) and it would crank on the key but not start. From this I concluded it was not getting the switched ground on pin 85 which is listed as "O186 ME7" and "H114 CU DME" (ie the "computer says yes" signal). I can force that one but the DME still says NO.
- Swapped rear tray relays 1 (MFI-DI) & 7 (Start-Lock) which were identical, no change.
- Relay 1 (MFI-DI) appears to be energised all the time even with key removed. I would have thought that would switch on only with ignition ON. I'm still working to understand other parts of the wiring diagrams to see if that seems correct.
- Relay 7 (Start-Lock) DOES ACTUATE immediately after turning on the ignition, but switches off half a second later. If I mash the key direct to the start position, the engine briefly cranks before the relay opens again. So all the high-current side is fine.
- With Relay7 (Start lock) removed and probing pin 85 (the switched ground which actuates the relay) I get some number of Megaohms with key off, then a change when key goes on, but goes to open circuit. I would think that should go to more or less zero ohms, providing a ground to switch the relay.
- I lifted the passenger seat and inspected the Alarm module, there was a tiny evidence of a spilt drink or similar on the floor, but all wiring and the module looked mint. Removed the module and inspected the board and it looks mint to the eye, no corrosion etc. Reassembled everything, still no crank.
Does anyone have any ideas of where a problem might arise other than the modules? Another relay somewhere? Are there any other tests I can run before pulling out the modules and sending them away? At least there does appear to be an Australian company (Injectronics) who advertises testing/repair, although there are a disturbing number of recent one-star reviews on google. The thought of having to replace the DME/Alarm/Keys at dealer prices terrifies me!
Sorry for the long winded post, appreciation if you've made it this far...
Steve
