Is my ECU goosed?

[chris1972]

I've managed to connect Rovergauge and get it running. The car has been running fine. However, I get a recurring fault code 29 ECU Checksum Error. The car last had a remap by Austec in 2011 when it had new injectors fitted plus a new ECU sometime before that. It is a non-standard Chip.

I have unplugged the ECU, cleaned the connections and reconnected, but the error returns. The car seems to run okay and I was none the wiser until I connected Rovergauge.

'Learned' advice and experiences appreciated... I'm feeling a little sensitive!

[blitzracing]

It may be bad remapping- the checksum is a very simple test of the binary data in the Eprom. If the mapping data changes with a remap- the checksum needs altering to match the new values stored in the chip. If its wrong it generates a checksum error- mind you the map is showing as 5, not the get you home map (I think thats 0 or 1) so its not put the ECU into fall back.

Interesting you say about the injectors- it could account for the long term trim being wrong if the basic map is out for the new injectors.

Edited by blitzracing on Thursday 18th April 12:22

[chris1972]

Mark

You're insight is valued and welcome! I went for a quick spin in the car and logged the run. I looked at the shorterm trim as I was driving and this seemed more on the plus side (didn't see any negative values) but did vary up and down. Everything else remained spot on. The adjustment factor remained around four squares.

Returned and sat on the drive. Within about 30 seconds the longterm trim zipped to -10%0 again. I turned off the ignition then. I've just noticed from your post that I should leave it running about 2-3mins. Will this value change or is this just odd behaviour.

When I phoned Austec a few months back to trace the car's history, I was told that it had new injectors fitted (called them again and am waiting more info). It did have a recon ECU in 2011. I think the injectors may have been done at a later date, but am waiting to find out?

Edited:

Austec are send some invoices in the post to me. It has 'redtop' injectors apparently? Will know more when I get the invoices through the post.

Edited by chris1972 on Thursday 18th April 13:02

[MADMAX2]

Mark i am in Cyprus till the weekend i will contact you after that to order rovergauge

[blitzracing]

The ECU has to have a stable platform for the basic level of mixture to be set. This is why it takes an idle period at full temp for a couple of minutes to get s reliable reading. The ECU will then keep this trim value in battery backed up memory so it does not have to reset it each time the engine starts. It will retrim each time the idle and temp allow, but the changes will be small once its been set once. With injectors with a larger through-put the whole map will need reprogramming and it all gets quite difficult as you make a change in the map, you then would have to wait for the long term trim to be set and check it was less than 100% before making any other changes- very time consuming, so I expect its been "overlooked". The fact that the short term trim is cycling means the ECU is still controlling the mixture within its limits, so the car will probibly drive OK and pass the emmissions tests, so you are none the wiser. In a perfect mapping world you will have very little long term trim, and then the short term trim only has to make small changes so getting the best MPG, driveabilty and emmissions. The 14CUX is a tough old beast and can throw something like + /- 20% fuelling corrections so you can get away with things being out of spec' in the first place.

[chris1972]

Thanks for that. I think the injectors were done in 2011 and the ECU replaced at a later date (will need to check receipts when they arrive). It does sound feasible that when the ECU was replaced it was done as a standard 5.0 Cat and the earlier installed uprated injectors overlooked.

I'm looking at de-catting and sorting out the induction. Is it worth remapping once I've done this or is it best to wait and then look at uprating the ECU next year to one of V8D's Megasquirt systems? I gather a 14cux map won't be cheap? Will it effect performance much?

I'm just relieved that my ECU doesn't appear to be goosed... thanks for your help.

Edited by chris1972 on Thursday 18th April 14:34

[chris1972]

Mark

I think you may be on the money with the map. Got the copy receipts today from Austec (two I had already.

2009 Top End Rebuild
June 2010 Red Top Injectors and Remap
Nov 2011 Recon ECU

I guess it was possible that the remap from for the injectors from 2010 wasn't put onto the new ECU in 2011 and it has a standard 5.0L cat map. Looking at the price of the map (£500 + VAT n 2010), I would be as well to purchase a P&P Megasquirt System for a few hundred more!

Will the Checksum error effect the reading of any other fault codes? I don't have any listed when I connect, but would like to know if this is the case.

Thanks again!