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DTC error 42 - fuel pump drive signal

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MDK87

Probationary Member
6
0
Jan 12, 2010
Brisbane, Australia
Hi lads, first post here after many years.
I've done a heap of searching and come across a few threads on here with great advice and instruction, however none of it has cured this problem.

I've got a pre-facelift GVR4 running an MD165808 (Jap-Spec RS) ECU. Pins 6 and 14 have already been swapped.

The car starts and runs, so the fuel pump is working and as such, I've ruled out the MPI relay but I went ahead and replaced IC109 driver IC anyway. Car still showed the CEL.

Had a look at the schematics and found that it's basically a feedback signal to tell the ECU that the fuel pump has power to it. Idk why that wasn't done internally off of pin 56 but anyway.
So I measured pin 13 with the car running, only 5V.
Found Steve's advice on some other threads here advising to connect pin 13 to ign 12V, so I did that. Traced the track back to diode D4 and measured 12V at it's terminal, so the track isn't o/c between there and the pin.
Reset the ECU, but the same DTC still shows up.

From that point, the circuit gets a bit out of my league. I'm starting to think that I'm going to have to forfeit the ECU, which kind of sucks because apart from the DTC, it is in completely working order. Has already been socketed, caps and bust M5269L drivers replaced (car idles great now!).
Besides, I would like to know what could cause that problem so that I don't ruin another ECU by throwing it in blind.

Any advice would be greatly appreciated.
Cheers.
 

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Since pin 13 is right off the fuel pump power feed, seeing 5v there doesn't bode well for the power to the pump.
Do you see battery voltage at the pump when it's running?
Do you see the same voltage with pin 13 disconnected from the ECU?

I haven't looked at the ECU circuit for this in years (plus not sure about the 808 differences) so offhand but based on what your saying it sounds like there is some wiring problem and perhaps some ECU issue.
 
Ahh, the man himself! Awesome.

Tbh I didn't think to check power at the pump because I had good fuel pressure but you raise a good point. I will check it with and without pin 13 connected to see if the ECU is pulling it down. Great advice, will report back shortly.

P.S - do you have schematics for the ECU?? I'd love to know where to get a copy..

Cheers.
 
Whilst the car is running, I'm getting 12V at the pump with and without pin 13 connected to the ECU.
Pin 13 of ECU connector to pin 2 of MPI relay connector didn't show continuity, so I cut the ECU wire to pin 13 and spliced it in with pin 2 of MPI relay.
Car still shows the same DTC..
 
do you have schematics for the ECU?? I'd love to know where to get a copy.
Nope, had to reverse engineer everything I was interested in.

Have you cleared the code or disconnected the power from the ECU since you reworked pin 13?
 
Yes I did Steve. The CEL pops back up within seconds of turning the engine over.
 
Duh, first link I click on from Google is an explanation from Jeff O (Keydiver) that the 808 ECU doesn't have it's circuits jumpered to support the fule pump feedback as required by the US software. What version are you running?
 
I'm actually using a Keydiver .bin file that I've touched up using TunerPro... But - I've loaded the stock Jap Spec .bin on it with only basic injector and MAF compensation altered and the CEL still lights up.

I've searched for ages on the topic with no luck. Are you able to link me to that page?
J103, J105 and R141 are silk screened on the PCB but not fitted. That is about all the feedback I can provide on that.
 
The keydiver chips are all based off of the E931 USDM code.

You have two choices, modify the hardware removing what makes the 808 ECU special or remove the code that causes the CEL.

I don't have the link to the GVR4 forum handy. I'll post it later and see if I can tell you what to no-op in the US code to eliminate the CEL tests.
 
You're right on there ^ mate.

I've been speaking with Kaxlon.
For future reference - to eliminate the fuel pump CEL test from the routine, he has advised me to change "5A" to "01" @ address 6988 in the .bin and I can confirm that it has worked for me. -> CEL no longer appears! :D
It seems like a pretty useless DTC anyway, you will know if the pump isn't running.
Obviously when you do this, make sure to reset your ECU to remove the saved DTC's.

I hope this thread might help someone in future, I couldn't find any info on this issue.

Cheers for the help fellas.
 
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