becm to ecm sync problem..... maybe

badbadrangy · Jul 1, 2013

1999 P38 4.6 v8
I have had a long drawn out battle with my p38 and im really hoping someone out there can help.
Engine turns over happily and there are no engine faults showing on the garages obd scanner. But it wont fire. I can force the fuel pump relay to activate with the computer but still no luck.
I can get the car to run fine if I short the fuel pump relay with a piece of wire but no windows or mirrors work.
I have replaced the relay and the fuse box.
The central locking works fine from the key but I think the fob is faulty because buttons dont work even with new batteries.
Alarm only beeps sometimes on locking.
Could this be a becm to ecm sync problem. There is nothing showing on the dash to say it is immoblised.

Datatek · Jul 1, 2013

You need diagnostics.

badbadrangy · Jul 1, 2013

Have had the garages snap on verrus connected and its not showing any errors on the engine. Is this piece of kit up to the job? could you recommend anything else?

Datatek · Jul 1, 2013

badbadrangy said:
Have had the garages snap on verrus connected and its not showing any errors on the engine. Is this piece of kit up to the job? could you recommend anything else?

Could well be loss of sync in that caseNanocom, Faultmate or Syncmate will re-sync it, There may be a member near you with the kit to do it if you put your location.

badbadrangy · Jul 1, 2013

Datatek said:
Could well be loss of sync in that caseNanocom, Faultmate or Syncmate will re-sync it, There may be a member near you with the kit to do it if you put your location.

Im in County Durham. up in the north east. If there is anyone up here that could help with a faultmate or syncmate, that would be prepared to help I would be grateful.

badbadrangy · Jul 1, 2013

really strange but ive just got the rangy to start 5 times in a row. without bypassing the fuel pump relay, then back to normal. doesnt fire.

eightinavee · Jul 1, 2013

Not a synch problem,if it were then shorting the fuel pump relay would make no difference.With Gems cars no synch inhibits cranking,injectors and sparks.Bosch cars no synch means cranking,but no sparks or injector pulses.
So clearly your car is synched.Whatever else is wrong with it will be found by basic electrical checks done with a multimeter using the wiring diagram.

badbadrangy · Jul 1, 2013

eightinavee said:
Not a synch problem,if it were then shorting the fuel pump relay would make no difference.With Gems cars no synch inhibits cranking,injectors and sparks.Bosch cars no synch means cranking,but no sparks or injector pulses.
So clearly your car is synched.Whatever else is wrong with it will be found by basic electrical checks done with a multimeter using the wiring diagram.

thanks for the reply. Am I right in asuming that if I can get it to fire up by bridging the relay, this problem probably isnt a faulty becm or ecm. also it runs fine so its not going to be fuel pump either.

Im concerned that the windows and mirrors dont work anymore since this problem appeared, are they controlled by the becm?

badbadrangy · Jul 2, 2013

also, i have feeling the garage swapped the relays around in the new fuse box, are all the yellow relays the same, can they be swapped around?

Datatek · Jul 2, 2013

badbadrangy said:
also, i have feeling the garage swapped the relays around in the new fuse box, are all the yellow relays the same, can they be swapped around?

All the yellow ones are the same. If a new fuse box was fitted, did they fit the correct one? There are several different versions. You can check for a signal from the BECM at the pump relay with a multi meter, likewise the ignition relay.

badbadrangy · Jul 2, 2013

Datatek said:
All the yellow ones are the same. If a new fuse box was fitted, did they fit the correct one? There are several different versions. You can check for a signal from the BECM at the pump relay with a multi meter, likewise the ignition relay.

I will try checking with a multi meter today. Thanks for your help

badbadrangy · Jul 25, 2013

Just an update all.
Turns out, the starting problem is down to the fuel pump not getting pressure up on the fuel rail. So the becm is turning it back off. The windows were down to a faulty switch unit. And the alarm/immobiliser issues were down to low battery. BECM is working fine.

ollyd · Oct 2, 2013

Hi, having very similar problems with my 98 4.6 HSE. Did you have to replace fuel pump or was it just a wiring issue?

mutsnutz · Oct 3, 2013

badbadrangy said:
Im in County Durham. up in the north east. If there is anyone up here that could help with a faultmate or syncmate, that would be prepared to help I would be grateful.

`try durham 4x4 mate i do believe they have one

jacckk · Oct 3, 2013

mutsnutz said:
`try durham 4x4 mate i do believe they have one

I assume he's fixed it since he posted this in July.

But I'm in County Durham and have Lynx diagnostics, haven't tried it on any other cars so I'm not sure if its locked or anything but I'd like to at some point!

mutsnutz · Oct 3, 2013

it wasnt till i posted when i realised the date of his last post :crazy: what are the lynx systems like are they any good heard mixed reviews about them

becm to ecm sync problem..... maybe

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