1996 P38 DSE ECU Replacement

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jimmacD

jimmacD

Well-Known Member
Posts
359
Location
Lincolnshire
Hi all!
Back to the ongoing issue with my P38 project car. Posted a few months back that I had a "no start" issue... no glow plug, engine cranked OK, healthy battery, healthy fuel pump etc.. etc.. Cleaned all the earths, bridged the fuel pump relay and she came to life and seemed fine? Back to a "no start" and now suspect that I have managed to spike the ecu? I have read a few posts about replacing the ecu and the symptoms. Should the amber engine management light come on during start up and then extinguish? My main question which peeps have covered but not answered.... "can I use my syncmate tool to connect a replacement ecu to the existing becm?" The previous owner said that the car had been "chipped" for performance... not hot start issues. The ecu has been in and out of the plastic box judging by the missing nuts and I can't find any external aftermarket gizmos so I assume the chip is in the ecu... this might have a bearing?
 
jimmacD said:
Hi all!
Back to the ongoing issue with my P38 project car. Posted a few months back that I had a "no start" issue... no glow plug, engine cranked OK, healthy battery, healthy fuel pump etc.. etc.. Cleaned all the earths, bridged the fuel pump relay and she came to life and seemed fine? Back to a "no start" and now suspect that I have managed to spike the ecu? I have read a few posts about replacing the ecu and the symptoms. Should the amber engine management light come on during start up and then extinguish? My main question which peeps have covered but not answered.... "can I use my syncmate tool to connect a replacement ecu to the existing becm?" The previous owner said that the car had been "chipped" for performance... not hot start issues. The ecu has been in and out of the plastic box judging by the missing nuts and I can't find any external aftermarket gizmos so I assume the chip is in the ecu... this might have a bearing?
Click to expand...
I'm not sure a syncmate will re-sync a different ECU but I'd be surprised if the ECU is the problem. Have you checked the fuel flow from the in tank pump?
 
I would have thought syncmate should do it, i spiked my ecu and had to change it and just had to write the ecu code to becm with my rovacomlite
so cant see why syncmate cant do the same as it just matches the ecu code to becm
if yours has been chipped you may be able to swap the chip to the new ecu.
 
brianp38dse said:
I would have thought syncmate should do it, i spiked my ecu and had to change it and just had to write the ecu code to becm with my rovacomlite
so cant see why syncmate cant do the same as it just matches the ecu code to becm
if yours has been chipped you may be able to swap the chip to the new ecu.
Click to expand...
Had a quick look at the ecu for usual suspects... corrosion, dry joint and blown capacitors. All seems OK, will take it apart properly and hunt for a chip, when I can remember where I left my torx thingies! I only have basic diagnostics and the syncmate. Tried local diagnostics chap who was more of a liability than a help. I can't see why the syncmate wouldn't work if I have match on replacement ecu, becm does all the security etc and the ecu should just respond with "wake up yer b%£&%rd!" from the becm?
 
Datatek said:
I'm not sure a syncmate will re-sync a different ECU but I'd be surprised if the ECU is the problem. Have you checked the fuel flow from the in tank pump?
Click to expand...
Hi again Datatek! This really seems a comms problem, in tank pump whirrs away happily when the relay is jumped. The ecu just isn't getting or reacting to the comms from the becm... no glow plugs, engine light etc.. which seems to point to the ecu? Fuel delivery etc.. I think is secondary to the main fault, no smoke without fire? My syncmate comes back with no ecu comms?
 
jimmacD said:
Hi again Datatek! This really seems a comms problem, in tank pump whirrs away happily when the relay is jumped. The ecu just isn't getting or reacting to the comms from the becm... no glow plugs, engine light etc.. which seems to point to the ecu? Fuel delivery etc.. I think is secondary to the main fault, no smoke without fire? My syncmate comes back with no ecu comms?
Click to expand...
A whirring pump does not mean it's pushing fuel through. The BECM just repeatedly sends the activation code to the ECU, nothing else, so worth checking connectors at the BECM and checking for wet carpet/underlay in the drivers footwell especially as yo have no comms. You could also try adding a wire from the engine ECU to earth.
 
Datatek said:
A whirring pump does not mean it's pushing fuel through. The BECM just repeatedly sends the activation code to the ECU, nothing else, so worth checking connectors at the BECM and checking for wet carpet/underlay in the drivers footwell especially as yo have no comms. You could also try adding a wire from the engine ECU to earth.
Click to expand...
Hi, done all that... earth wire on ecu, checked for wet, eaten wires and becm.... going to have another check of power/ignition feeds to ecu. My gut tells me that its the ecu and most with same symptoms ended up changing ecu after spending out on everything else. Thought I would start with the cheapest first.
 
Checked power coming into ecu with RR ignition off and on. Becm is sending low volt signals and healthy current so that part of the system seems to be working and it points towards the ecu being faulty. Now in the process of sourcing another automatic non egr ecu... some sellers seem to think they are made of gold dust judging by the broad range of prices? My understanding is that they rarely go wrong and in theory should be the right side of £40 like all the other P38 and BMW ecu. A few posts have possibly answered my original question..."can I use syncmate to introduce a replacement ecu to the becm?" It seems that you can use syncmate.
 
Ecu ordered and should arrive next week, probably setting myself up for disappointment? Haven't had a huge amount of luck lately with stuff off the interweb.... wrong lower arm for my A6, wrongly described centre caps for my van and a P38 boot actuator which turned out to be for a door! I think with COVID more peeps are using interweb selling and the numbers of poor sellers has increased dramatically?
 
Family went down with COVID so stuck in doors for a while. Replacement fuse box arrived, fitted with everything crossed that it would solve my "non start" issue! Nope, still have a non starting early P38 DSE? Local breaker recommended looking at the glow plug relay but that looks fine to me. Power is getting through on the shiny fuse strip, no visible corrosion etc.. Is there more to the relay which might have failed? Any ideas where to go next? Somes have suggested the engine side fuel pump electrics but I can't see anything electrical on the pump, the in tank pump is fine?
 
jimmacD said:
Family went down with COVID so stuck in doors for a while. Replacement fuse box arrived, fitted with everything crossed that it would solve my "non start" issue! Nope, still have a non starting early P38 DSE? Local breaker recommended looking at the glow plug relay but that looks fine to me. Power is getting through on the shiny fuse strip, no visible corrosion etc.. Is there more to the relay which might have failed? Any ideas where to go next? Somes have suggested the engine side fuel pump electrics but I can't see anything electrical on the pump, the in tank pump is fine?
Click to expand...
Have you checked you are getting power to glow plugs as soon as you turn ignition on? This will prove if relay is working or not.
have you checked for duff glow plugs?
 
Rubberknees said:
Have you checked you are getting power to glow plugs as soon as you turn ignition on? This will prove if relay is working or not.
have you checked for duff glow plugs?
Click to expand...
I have no engine light or glow plug symbol when starting which makes me think it is a wiring/comms issue rather than failed components. My syncmate.. doesn't and comes back as no comms with ecu? I have replaced the ecu, fuse box. I think it is possibly a damaged wire in the loom but where to start looking? I don't think the P38 becm/ecu is subtle enough to identify a glow plug failure one or all? I will check the plugs for voltage.
 
jimmacD said:
I have no engine light or glow plug symbol when starting which makes me think it is a wiring/comms issue rather than failed components. My syncmate.. doesn't and comes back as no comms with ecu? I have replaced the ecu, fuse box. I think it is possibly a damaged wire in the loom but where to start looking? I don't think the P38 becm/ecu is subtle enough to identify a glow plug failure one or all? I will check the plugs for voltage.
Click to expand...
OK
 
Grrrrrr said:
Got to be a break somewhere.
Click to expand...
Does seem to point towards a break somewhere? There is a small bit of previous rodent damage on driver side bulkhead/bonnet foam, it didn't look like anything serious as no holes or damage into the cabin/dash. I think I will start there and just work my way through the wiring loom. I keep meaning to download RAVE and a wiring diagram. Don't know why Haynes never published a manual for the P38, probably one of the most worked on vehicles produced by Land Rover? Series LR just needed a big hammer and Classics, Discos etc.. hammerite! The P38, Engineering degree! Even my L322 and Gaylander are easier to fault find... just plug them in.
 
jimmacD said:
Does seem to point towards a break somewhere? There is a small bit of previous rodent damage on driver side bulkhead/bonnet foam, it didn't look like anything serious as no holes or damage into the cabin/dash. I think I will start there and just work my way through the wiring loom. I keep meaning to download RAVE and a wiring diagram. Don't know why Haynes never published a manual for the P38, probably one of the most worked on vehicles produced by Land Rover? Series LR just needed a big hammer and Classics, Discos etc.. hammerite! The P38, Engineering degree! Even my L322 and Gaylander are easier to fault find... just plug them in.
Click to expand...

I think if you unclup the expansion tank and look underneath there's a plug under there where @tomcat59alan found a break in the past. Good place for a rodent to nibble too.

I saw a woodmouse in one of mine the other day. Bit nerve racking!
 
jimmacD said:
I have no engine light or glow plug symbol when starting which makes me think it is a wiring/comms issue rather than failed components. My syncmate.. doesn't and comes back as no comms with ecu? I have replaced the ecu, fuse box. I think it is possibly a damaged wire in the loom but where to start looking? I don't think the P38 becm/ecu is subtle enough to identify a glow plug failure one or all? I will check the plugs for voltage.
Click to expand...
If you have changed the ECU and have no comms you will never start it as you cannot sync the ECU and the BECM to unlock the immobiliser.
 
Datatek said:
If you have changed the ECU and have no comms you will never start it as you cannot sync the ECU and the BECM to unlock the immobiliser.
Click to expand...
??? The ecu is same as old and should resync, I don't think it has any effect on the immobiliser, that's more to do with the becm. It isn't immobilised, cranks etc.. just nothing going on with the ecu, same as old one with "ecu not waking up" from syncmate. That is the frustration... it's not one of the usual faults, no codes, no warning lights. I think it is a physical break somewhere rather than a coding issue.
 
jimmacD said:
??? The ecu is same as old and should resync, I don't think it has any effect on the immobiliser, that's more to do with the becm. It isn't immobilised, cranks etc.. just nothing going on with the ecu, same as old one with "ecu not waking up" from syncmate. That is the frustration... it's not one of the usual faults, no codes, no warning lights. I think it is a physical break somewhere rather than a coding issue.
Click to expand...
When an ECU is changed on the diesel you have to re-sync it.
 
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