Mk 4 Mondeo ECU Comms issue

[Buckc02]

Hi, I am not an experienced mechanic in any way so any help would be gratefully received.
I have changed the engine (2L Diesel) in my 08 Mk4 mondeo as all but 2 of the rocker arms were snapped on the old one and I was advised that the engine could have many things wrong with it, I saw the donor engine running before it was removed.
I swapped the engine out myself (thank you YouTube for the assistance) and have everything connected.
I have the injectors from the old engine but I have left the original ones in the replacement engine but not had them reprogrammed to the ECU.
When I turn it over it cranks but does not fire, I have had a diagnostic test done on it and there it says that there is a communication error on the ECU, I have tested the voltages to the ECU and they seem to be ok (again thanks to YouTube)
I have checked every connection to the engine, all the fuses and the relays and stripped the wiring to the Y point on the loom looking for damaged/broken wires but all looks ok.
As an enthusiastic but not very experienced amateur mechanic at best I am now stuck, I am assuming not having the injectors programmed wouldn't cause this.

any ideas on what I can try next (other than take it to a garage)

[stevieturbo]

There is no reason changing the engine should affect your ability to communicate with the ecu, the original ecu on the car. Were you able to communicate with it before the work ?

[Buckc02]

Everything worked until the rocker arms snapped as I was driving down the road, I’ve put the replacement engine in and now it won’t communicate.

[stevieturbo]

Can you communicate with any other modules on the car ?

[Novexx]

Are you using the pump from the new engine?

[Buckc02]

As far as I am aware everything else was being communicated with. I am using the pump that came with the replacement engine, should I swap it with the pump off the old engine?

[Belle427]

Just make sure you have the power and ground at the ecu.

[Novexx]

Buckc02 said:

As far as I am aware everything else was being communicated with. I am using the pump that came with the replacement engine, should I swap it with the pump off the old engine?

I think I've given you a bum steer on that one (sorry), looks like the TDCI pumps don't require coding.

Do you know what the specific error message was or if any DTC's were advised?

[Zener]

Check for a 5 volt reference at say the cam sensor or air mass sensor etc with ignition on if you have no 5 volt ref then the ECU is not receiving power and explains no comms issue , then you can check your power and earths etc to ECU or failure of ECU ...Unlikely IMO , you may have damaged or disturbed the loom or such like ..........check fuses?

[Buckc02]

Hi. I’ll get the system diagnosed again to see if there are any other errors.
I have voltages to the ECU (12v) where I think there should be. I have checked EVERY fuse and swapped all the relays about.

[stevemcs]

Injectors do need coding, do this and see what happens.

Are you sure it’s the correct engine for the car
If it ran before you fitted it then you have either missed something or something is wrong
When we fit used engines we swap everything over from the old engine, that way we know everything worked before so should still work.
That includes all looms and sensors
Did you check the timing on the new engine was it correct ?

Edited by stevemcs on Saturday 19th March 13:51

[Zener]

Buckc02 said:

Hi. I’ll get the system diagnosed again to see if there are any other errors.
I have voltages to the ECU (12v) where I think there should be. I have checked EVERY fuse and swapped all the relays about.

Read above you still need to confirm ECU voltage out (to sensors etc) to confirm ECU is or isnt alive

[stevemcs]

Also does it start if you try a couple of squirts of easy start in the induction system.

I would also refit your old injectors. I assume the engine was replaced as the belt had failed.

[Polly Grigora]

Have you a diagram of the engine and ECU wiring that you are able to post here?

[stevemcs]

Polly Grigora said:

Have you a diagram of the engine and ECU wiring that you are able to post here?

I think op needs to back to like for like before following the ecu issue, it might be historic. At the moment it has the wrong injectors and uncoded, it ran before as did the new engine either something isn’t compatible or it’s fitted wrong

[stevieturbo]

stevemcs said:

Injectors do need coding, do this and see what happens.

Are you sure it’s the correct engine for the car
If it ran before you fitted it then you have either missed something or something is wrong
When we fit used engines we swap everything over from the old engine, that way we know everything worked before so should still work.
That includes all looms and sensors
Did you check the timing on the new engine was it correct ?

Edited by stevemcs on Saturday 19th March 13:51

Can't code, if you cannot communicate.

Although it does seem we're getting 3rd party information for a lot of stuff here.

Timing not important yet....if the ecu appears dead ( which is rather unlikely unless they've blown it somehow during the works )

We still have not had proper clarification if other modules on the car can be seen, or even if there were comms prior to all this work.

Checking for a 5v reference at a suitable sensor is a sensible idea, and would give some indication if the ecu itself is alive.

[Polly Grigora]

stevemcs said:

Polly Grigora said:

Have you a diagram of the engine and ECU wiring that you are able to post here?

I think op needs to back to like for like before following the ecu issue, it might be historic. At the moment it has the wrong injectors and uncoded, it ran before as did the new engine either something isn’t compatible or it’s fitted wrong

Have you a diagram of the engine and ECU wiring that you are able to post here?

[Buckc02]

Hi, apologies for the lack of response.
Not going to get chance to look at anything for a few days due to being at work. As soon as I get more time/info I’ll post answers and finding.
Thanks loads for the help so far

[Polly Grigora]

Am wondering if disconnecting the battery has caused a problem

Would be good to take a look at a diagram though

[Polly Grigora]

Any update?