A rare ECU failure, something that’s becoming more common in Volvo P80 models as they age. Here’s what it looks like from a diagnosis viewpoint.
Ozark Lee »
The saga of the new XC continues and I’ve managed to get myself tied in a knot. I don’t know which way to go to get the car to reliably start since I have a bunch of conflicting diagnostic tests. I suppose this is, more or less, directed to Mike but I need the collective genius of the board to get through this.
I bought the car cheap ($1300 Cash) knowing that the fuel pump was bad. The car is otherwise on very good shape with only 125k on the clock. My other 1999 XC met an untimely demise due to a drunk driver and is now a parts car, parked behind my mother’s barn, but a couple of weeks before the other XC got totaled I put a new fuel pump in it. I just pulled the recently replaced fuel pump from the parts car and installed it in the new car.
After the fuel pump was changed the car started and ran fine but I had the flashing ECC lights so I fired up VOL-FCR to see what the ECC was mad about. VOL-FCR couldn’t really deal with the car from the menu so I just told the program it was a ’98 rather than a ’99. VOL-FCR couldn’t read anything and I tried to probe nearly all of the systems with it. After that episode the car didn’t want to start but that was really only the third or fourth time I had even tried to start it since replacing the fuel pump. It could be significant or it could be a coincidence – I don’t know. After a few attempts (it could be 2 or it could be 30) the car will start and at times it will exhibit a start and promptly die condition that would be typical of a bad antenna ring. After it starts, if there were several attempts, it will sputter a bit until it cleans up the excess fuel from the failed starting attempts. The car has yet to set a P code for anything and it never set a P1670.
Ozark Lee »
The battery cable had the end chopped off and a cheap auto parts store connector added to it so I changed the battery cable with one from the parts car. That was its own special nightmare and I ran out of daylight yesterday getting that done. I knew it wasn’t going to change the situation but it needed to be done anyway.
The car is back to all of the modules that came with it. The grounds from the cam cover to the firewall are both good as is the negative battery terminal to the block and the secondary ground from the battery to the chassis. For some reason an additional ground was spliced into the ECU harness where it goes to pin A-54. That pin should be at ground anyway and it and pin A-53, which ties to the same ground point (31/71), both show a solid ground with 0.0 ohms to the block.
The alarm does in fact work. I was unaware of the delay so I locked the door and gave it about 10 minutes and when I opened the door through the window the horn sounded.
Things do get stranger though. I did some more tracing with the oscilloscope and I find that the injectors always pulse, whether the car starts or not. I’m not sure if the immobilizer is supposed to kill the ignition or the injectors or both. The injector pulses always seem to be there. The trigger signals to the coils, it turns out, are there sometimes even when there is a no start condition. They are, of course, always there when the car does start but there seems to be no rhyme or reason as to why they are there sometimes and the car won’t start and without them there the car, as expected, won’t start. The battery voltage is always steady on the red wires to the coils and the coil grounds are clean and tight on the cam cover.
I have some screen grabs of the VIDA diagnostics as they apply to the IMM, the VLGA, and some information from the ECM.
I noticed one other odd thing that was not consistent. After some time (as in 20 or 30 minutes) with the door open the relays on the VGLA modules start to click and the dome lights cycle from off to bright through a dimming cycle. This happens (both the relays and the light) at about 1.5 second intervals.
The antenna ring is brand new, the connections look clean on both the antenna ring end and on the IMM module end, and I gave both ends a shot with CRC contact cleaner. On several occasions though the car does act exactly like it has a bad antenna ring in that it will fire and immediately die.
The car always cranks, at least until I manage to run the battery down and then I put it back on the charger overnight.
Once again, it seems when I pull a spark plug and lay it on the head with the coil, and it doesn’t seem to matter which one, the car will start pretty reliably. I did find some solder globs around coil number 2 but I think it was some sloppiness from splicing the wires to the CVVT valve which looks like it was recently changed. Recent is somewhat relative as I think this car had been parked for over a year at the repair shop where I bought it.
I have changed both the number 1 and 2 coils with known good replacements. The spark is orangish rather than blue with the spark plug laying on the cam cover.
I never could hear the deadlocks engage after the door was closed and locked.
As far as the signal and relay states and signal states go I don’t know if some of them should be opened or closed, low or high. They don’t seem to change between the starting and not starting conditions.
If anyone sees something on the screen grabs that stands out please let me know.
The Solution — Dead ECU
Ozark Lee »
At long last the saga is over.
I shipped the ECU and the parts car ECU to Lucky and had him clone the “new” car into the parts car ECU. Other than the battery being totally dead after months of being parked it starts first time and every time!
I have never had an ECU fail intermittently like that. For that matter, I have never had an ECU fail at all.
I sure am glad to have this one in the done column and it is just in time for the predicted snow storm.
1999 V70XC I’m stuck – I need ideas.
