V6 Engine will not crank over but will start if I bypass the starter relay.

[dwae01]

Although this is an old thread I thought I would add to the store of useful information. My VZ also developed this fault after being off the road for about 6 weeks. I had replaced the heads due to a burnt out valve and when I had finished I could not start it. Finally tracked the problem down to no earth being supplied to pin 86 by the ECM. With the information supplied by this forum I am about to endeavor to supply a permanent earth to this pin before I start to lay out big money on another ECM. Symptoms were all similar to what has been described above. Wish me luck

 

[dwae01]

Well it worked. I put a short piece of wire onto pin 86 on the start relay and connected it to the negative side of the battery which is nearby. Car started straight away. Will now need to investigate the ramifications of this work-around. If there is nothing too serious I will probably make this connection permanent rather than pay the $1000 to $1500 to my friendly Holden dealer. Might need to investigate the market for a second hand ECM assuming I could get it reprogrammed. Has anyone had any experience with this?

 

[dwae01]

Spoke too soon. Started instantly then died but starter motor kept turning. Good to see it come to life if even for a couple of seconds. Back to the drawing board.

 

[dwae01]

Another step forward. Jumped across pins 87 and 30 on Start relay with ignition on. Replaced relay once car had started. Car runs perfectly. Getting an SVS (spanner)and a Power Train (engine with lightening bolt) error messages. Only problem is that I have to do this every time I want to start the car. Any suggestions?

 

[alloytec sludge]

i had the same problem and was shorting out the terminals 30 87 to get it started ran beautiful for one day next day went out and it was running rough

 

[morphix]

Another step forward. Jumped across pins 87 and 30 on Start relay with ignition on. Replaced relay once car had started. Car runs perfectly. Getting an SVS (spanner)and a Power Train (engine with lightening bolt) error messages. Only problem is that I have to do this every time I want to start the car. Any suggestions?

I had this same thing occur a year or 2 back when my ECU shat itself, along with the SVS and Power Train error messages.

When this was occurring, hooking up a scan tool showed lost communication to the ECU, it might work for a bit, then does it again.

 

[dwae01]

Finally got the car running properly. I had two faults (both caused by me). The local autoelec told me that the ECU gets its earth from the gearbox. I assume this is why the car will only turn over when the car is in Park or Neutral. So he suggested I check the connections in the loom between the ECU and the gearbox. Sure enough at the very back of the head (in my own defence it was under a lot of hoses going the LPG system) I found a four pin connector that I hadn't reconnected. This solved the "not turning over" problem. Then I had a sudden drop in power (limp home mode) which occurred after about 5 minutes driving. It was so severe that the car struggled to get up a hill to get me home. Found another connection that I had not reconnected properly. At the very back of the RHS head there is an earth strap that goes to the loom connecting the fuel injectors (more hoses in the way). I had connected it to another location because I could not find the original hole (perhaps it was not in the replacement heads??). When I shifted it I had not done up the nut tight enough. I was alerted to this when I connected up a Tech 2 and it reported injector faults in cylinders 1, 3 and 5. So all good now. Hope this is useful to someone. I now have a Tech 2 that I am willing to connect to another 1997 - 2011 GM vehicle if you are desperate and live north of Melbourne.
DK

 

[morphix]

Glad to see it was stuff that was just overlooked rather than costly $$$ to repair.

 

[alloytec sludge]

finally got my car scanned today
u2105 can bus:engine control unit communication error
u2108 can bus abs control error
u2106 transmission control unit can data bus
u1304 data line. k bus
u2105 can bus engine control unit
need new or repaired e c u

 

[morphix]

Yep, i was getting the same symptoms and same messages, new ECU.. it cost me just over $1300 ($1385 or so iirc)