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Discussion Starter · #1 ·
Hi all,

I'm new to the forum. I've just replaced the head gasket on my wife's 10-plate Zafira 1.6 XER after it overheated but now can't start the car. The service light is on & nothing happens when I turn the key. My OBDII reader connects to the plug-in unit but then won't connect to the ECU so I can't get any fault codes. The fuses all look ok & there's no sign of water in the UEC. How do I get the ECU to communicate? I have the security code but no idea how to input it if that's the issue.
 

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You don't need the sec code to communicate with the ecm,
which light do you call the service light ?
did you remove the ecm connectors when doing the head ?
 

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Discussion Starter · #3 ·
The car symbol with a spanner through it. And yes I removed the ecm connectors and the ecm itself to get the intake manifold.
 

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Is the light flashing with ignition on ?
 

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I'd remove the ecm connectors again and carefully check all is ok and no bent pins
 
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Discussion Starter · #8 ·
I don’t think so - the one to the ecm and at the rhs of the cylinder head are connected properly.
 

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Discussion Starter · #10 ·
Ok - I’ve checked the pins & they’re not bent. I also cleaned up the earth connection but still nothing.
 

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My sisters zaf 1.8 would have intermittent starting problems, turn the key and nothing, after a little digging i found a heavily corroded wire in the loom where it goes over a bracket on the gearbox side of the engine, it was the supply to the ecu so we couldnt communicate with it, Not saying thats what your problem is but worth checking.
 

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Does your OBD thingy connect to any modules on the car?
 

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Discussion Starter · #13 ·
It’s an ELM327 type code reader using the Car Scanner app. I can only see successful connection to the ELM & failure to connect to the ecm. Maybe a different app would give more options?
 

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ok you need to work through what you've done and make sure it's not something really silly
(cos it often is)
but first what's the battery voltage ?
 
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Discussion Starter · #15 ·
I put a brand new battery on yesterday as I thought that could be part of the problem. Through the hidden menu I’m getting 8.7V.
 

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ah about 4 volts shy then,you really need to go over all the connections
 
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Discussion Starter · #17 ·
The battery seems to be draining when I leave it connected up - the central locking has just stopped responding. I’ll put it on charge for a while.
 

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You have three main grounding points to the chassis between the uec and the battery tray. The closest to front is irrelevant as it is grounding for reverse gear sensor. The remaining two might be worth checking. Also old woes with the uec. But first and foremost is correct battery voltage.
You might find that after headgasket job you have broken wires within the corrugated trunking on the right side of the engine. It goes directly between the uec and ecu, easily fully removable. The wires are rubbing against the corrugated walls, removing slowly their insulation which leads to corrosion and all host of problems. Sometimes, as I discovered it the hard way this week, they are visible only when fully removed from that trunking.
 
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