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Ford Scorpio 2.9i BRG engine OBD1 fault code issue.

Ford Scorpio 2.9i BRG engine OBD1 fault code issue.

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Scimitarinjection

Original Poster:

13 posts

5 months

Tuesday 8th August
quotequote all
I have had this car for a few months and steadily finding my way around all the problems. I bought it blind from someone who must have been describing a different vehicle in his advert, but I digress.

The one issue that I am unable to find is during KOEO (Key on Engine Off) preliminary tests. Here I am getting a fault code of 76 which on all of the tables I have looked up, refers to VAF no response during dynamic test. Now there are two issues with that, a) The engine isn't running during KOEO testing so of course there will be no response and b) This car doesn't have one anyway as the BRG build is HEGOs and MAP sensors! The suggestion by a Ford "expert" that is down to the code reader is nonsense as OBD1 only toggles an output line, so the codes can only be coming from the ECU. That having been said, he was still in nappies when the car was built. ;-) I have tried three different code readers (one of which I built myself) just to humour him.

Much testing has been done, most documented over at the specialist forum: http://granada-and-scorpio.com/phpbb/viewtopic.php... with no more clue about what is going on. The ECU has been swapped, the complete engine loom has been rebuilt, engine serviced, HEGOs replaced and ECU identity confirmed as correct for this build. MAP sensor has been tested and produces the expected variation of signals. Vacuum lines have been checked and double checked, some being replaced anyway.

The code sequence when read is 10, 10 , 76, 76 and 11. So we get an all clear at the end. Erasing the fault codes does not work, most likely because the fault is generated the moment the ignition is switched on.

KOER (Key On Engine Running) tests now pass after the HEGOs and wiring were replaced.

So any clues please?

GreenV8S

24,916 posts

208 months

Tuesday 8th August
quotequote all
I don't know anything about that ECU, but I know that on the 14CUX I used to have the ECU used an external tune resistor built into the ECU loom to select options within the ECU. A wiring fault or incorrect resistor would cause various errors and misbehaviour within the ECU as it tried to use a mode which was inappropriate for the engine hardware. Is it possible your ECU needs something similar?

Scimitarinjection

Original Poster:

13 posts

5 months

Tuesday 8th August
quotequote all
GreenV8S said:
Is it possible your ECU needs something similar?
Useful suggestion, but the circuit diagrams etc show nothing in the way of additional components or shorting links. As far as I am aware, the options are purely set in software and the part number then changes to suit.