A long time since I worked on these vehicles, but I'll try and help a little. If you can lock and unlock the vehicle with the remote, then the becm is happy with the code it is receiving and the two units are synchronise and the eka code is not reqd. When you put the key in the ignition and turn on the ignition you should see the red LED flash once on the remote. If the red LED continues to flash then the becm is not receiving the rf signal from the remote or it is not happy with the code. In this situation you will then get the Engine immob
.etc message. When everything is working ok, then when you turn the key to ign II position, the LED will flash once, the becm checks this code and sends a fixed security code to the GEMs ecu. If the GEMs ecu is happy with the security signal, it sends a signal back to the becm. When the becm sees this signal, it puts the mil light on and the Becm will allow cranking of the engine. The GEMS does not control cranking. If the red led is not continuously flashing then the becm is happy with the security code, but if the mil light is not on then the becm is not seeing a Im happy signal coming back from the Gems, so engine will not then crank.
Im 99% sure that the GEMS only inhibits fueling and not the HT system when it has not seen the code from the becm.
If the engine is cranking and there are no sparks or fuel then it could be the crank sensor, but I would check the 3 Gems ECU connectors first (includes the crank sensor input). The connector terminals are prone to opening up. In my tool kit, the 2nd most useful tool after the multimeter is a set of male connector pins. Whenever Ive work on a P38, Ive always checked the female connector terminals for opening up by probing with the corresponding male pin to see if there is an interference fit or not (not is bad). If you think that the crank sensor is damaged then that is very easy to see when you remove the sensor. The pin will be bent or heavily scored with lots of metal filing attached.
Im 99% sure that the GEMS only inhibits fueling and not the HT system when it has not seen the code from the becm.
If the engine is cranking and there are no sparks or fuel then it could be the crank sensor, but I would check the 3 Gems ECU connectors first (includes the crank sensor input). The connector terminals are prone to opening up. In my tool kit, the 2nd most useful tool after the multimeter is a set of male connector pins. Whenever Ive work on a P38, Ive always checked the female connector terminals for opening up by probing with the corresponding male pin to see if there is an interference fit or not (not is bad). If you think that the crank sensor is damaged then that is very easy to see when you remove the sensor. The pin will be bent or heavily scored with lots of metal filing attached.
Thanks for the info. You are pretty much 100% confirming what I have been thinking that the GEMS ECU is not talking to the BeCM. Have replaced crank sensor and old one looked fine had not been physically damaged. The wiring to sensor may well not have continuity will check. Have heard BeCM inhibits cranking but GEMS does not so good to hear someone else saying it.
Engine check light is not coming on at moment since battery replacement and not cranking but this took long time to come on after initial breakdown which could be explained by a dodgy feed to GEMS. Light was often blinking before going on properly also. Still going to replace fuse box as ordered new one and have some burning and loose terminals in mine. Also replacing battery as mine is well under recommended output.
I think a poor earth or power feed to GEMS ECU might have caused the delay on mil light and the flashing. Might also explain why at moment it won't come on at all if dodgy wiring to GEMS is the cause. Will check light on key when in different key fob positions tomorrow.
Fairly sure that at moment GEMS is not sending back to BeCM but before it was doing so after a delay.
Engine check light is not coming on at moment since battery replacement and not cranking but this took long time to come on after initial breakdown which could be explained by a dodgy feed to GEMS. Light was often blinking before going on properly also. Still going to replace fuse box as ordered new one and have some burning and loose terminals in mine. Also replacing battery as mine is well under recommended output.
I think a poor earth or power feed to GEMS ECU might have caused the delay on mil light and the flashing. Might also explain why at moment it won't come on at all if dodgy wiring to GEMS is the cause. Will check light on key when in different key fob positions tomorrow.
Fairly sure that at moment GEMS is not sending back to BeCM but before it was doing so after a delay.
Done a bit more research and it all seems to tally with what I am being told on here. Looks like my Engine ECU and BeCM are out of sync but as can't get re-sync to work it looks like Engine ECU has a power problem. Will check pins on ECU and replace fuse box when it arrives.
Seems a bit strange that engine check was coming on after a long delay and some flashng before and that it ended up cranking even when the check light did not come on. I guess when your dealing with complex electronics like this you can get all sorts of results due to same fault.
Seems a bit strange that engine check was coming on after a long delay and some flashng before and that it ended up cranking even when the check light did not come on. I guess when your dealing with complex electronics like this you can get all sorts of results due to same fault.
mozz smith
Well-Known Member
hi , if your still struggling give me a ring , ive sent you a p.m. with my no cheers MOZZ 
To check the connection between the GEMS & BECM, go to the GEMS ecu and wriggle the wire (from memory think it was a black wire)when ignition turned on and get someone to tell you if the amber check engine light comes on.
I've not been on this site for a while but I can recall from before from others that if the battery slowly goes flat that this can cause the becm to put out an incorrect code to the GEMS, maybe others can remember this. Fix I believe was to borrow a diagnostic box to reset the code. But before you spend more money, do the easy stuff like checking the connections on the GEMs ecu. You can also check the black wire at the becm end. Good luck.
I've not been on this site for a while but I can recall from before from others that if the battery slowly goes flat that this can cause the becm to put out an incorrect code to the GEMS, maybe others can remember this. Fix I believe was to borrow a diagnostic box to reset the code. But before you spend more money, do the easy stuff like checking the connections on the GEMs ecu. You can also check the black wire at the becm end. Good luck.
Rick-the-Pick
Active Member
This is an interesting thread.
Just recap me on a few things.
Is the engine cranking? Fobs unlocking doors?
Just recap me on a few things.
Is the engine cranking? Fobs unlocking doors?
Hi, key fobs have always worked but bit hit and miss on occasions. Doors except passenger front work off fobs and key. Engine did not crank on first attempt but after a while engine check light started coming on after 20 or 30 second delay and would crank but no spark or fuel. After a while would crank even when light did not come on.
Tried sync-mate but failed to communicate. Towed home and took battery out to charge. Battery was low and very underrated compared to factory spec. Checked fuse box found Diode D1 black and blower relay terminal loose. Re-connected battery, fobs still work after placing in ignition but engine check light won't come on and won't crank.
Sync-mate still gives one red flash won't communicate.
Tried sync-mate but failed to communicate. Towed home and took battery out to charge. Battery was low and very underrated compared to factory spec. Checked fuse box found Diode D1 black and blower relay terminal loose. Re-connected battery, fobs still work after placing in ignition but engine check light won't come on and won't crank.
Sync-mate still gives one red flash won't communicate.
Rick-the-Pick
Active Member
Did you say you have a new fuse box arriving shortly?
Datatek
Well-Known Member
He did
mozz smith
Well-Known Member
hi olly i was away yesterday but am at home now available any time cheers mozz
Did a run through with Mozz today and established I have old style RF receiver which had been disconnected. Also possibly have dodgy micro switches in drivers door lock. Still don't have replacement fuse box but have new battery on.
Noticed black wire to EMS is very stretched over the red plug but decided against poking probes into it in case I damage the electronics. Am getting cranking occasionally after I press down on relays. No engine check light coming on.
Now looking into finding someone with diagnostics.
Noticed black wire to EMS is very stretched over the red plug but decided against poking probes into it in case I damage the electronics. Am getting cranking occasionally after I press down on relays. No engine check light coming on.
Now looking into finding someone with diagnostics.
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