Electrical Fooling the ECU

BeaverMeat · Sep 10, 2021

This is a 5.0 swapped Volvo… I need to trick the computer so I can install an engine light and have it work properly. It’s showing two codes because of the swap. Secondary fuel circuit fault and clutch position sensor fault.

I have no idea where to start to find where the wires go from the ECU. Some of wires on the pigtails have been cut off flush. Where to start? Lol

Mustang5L5 · Sep 10, 2021

What ECU are you using?

if it’s any of the A9x family, you just need to run a wire from pin 19 to any part of the fuel pump relay circuit that sees power when the pump is active, usually the wire that closes the relay will do fine. The ECU just wants to see that the fuel pump circuit is on.

As for your other problem, what’s the code number? Is it 67?

BeaverMeat · Sep 11, 2021

It’s 1989 hardware.

Yes. Code 67.

The Volvo clutch pedal still has the switch. I may just connect it if compatible. Just need to find what wire it is from the ECU

As for the pump secondary circuit (code 96)… this is going to be a mess. lol. So what you’re saying is pin 19 isn’t part of the fuel relay circuit? I just have to Hotwire it.

Thanks for the reply.

Mustang5L5 · Sep 11, 2021

Pin 19 is just a monitoring wire.

let me dig up some wiring diagrams later in that day that will help explain further. I haven’t quite memorized all the wiring for these cars just yet.

Mustang5L5 · Sep 11, 2021

Here’s a wiring diagram.

As you can see, pin 19 is just monitoring the fuel pump relay to see that it’s closed. I’m not sure how you are running the pump setup on your car but any 12v key-on source should fool it.

Mustang5L5 · Sep 11, 2021

As for code 67, that’s a bit trickier to solve. Mustangs we’re wired differently depending on the trans and ecu. That’s why I asked what ECU you were running.

It’s tied to pin 30, but it behaves differently depending on auto or manual

I assume 5-spd here? If so, pin 30 it wired in parallel to a clutch sense switch and the trans nuetral sense switch. If either closes it tells the ECU the car is in nuetral by way of clutch pushed in or trans in nuetral. This closes a pin 30 to ground loop.

I could suggest to try something but without knowing how pin 30 is wired now and if it’s an auto or manual ECU I’ll hold off

BeaverMeat · Sep 11, 2021

It’s a T-5

do you have a wire color code? lol. I know what BK is… what the heck is PK? Pink?

7991LXnSHO · Sep 11, 2021

PK/W

BeaverMeat · Sep 11, 2021

lol.

thought so… just confirming. This is the green relay in the interior? The other relay under the hood is the inertia relay?

Mustang5L5 · Sep 11, 2021

It would be under the drivers seat up to 1992. 1993 was under the MAF

BeaverMeat · Sep 11, 2021

Well this is goofy AF.

I have the E5DB-11433-A2A relay on the same harness as the MAF like the 1993. I also have the green pigtail (with the pink/black wire) next to the ECU with no relay on it. I think that’s the problem.

‘89 engine with a ‘93 harness for the fuel/maf/airbags. It does have the two crash sensor pigtails.

BeaverMeat · Sep 11, 2021

My ecu is a e9zf-12a650-a2a a9l. Which means a ‘89-92

BeaverMeat · Sep 11, 2021

Edit… I guess that’s the WOT relay. Yeah, I’m a noob. lol. I don’t have A/C so I guess I can eliminate that… maybe. Idk.

I guess the computer isn’t detecting a fuel pump because the relay isn’t there. lol.

The engine is 90+ considering it has the airbag sensor connectors. (two white round connectors. 2 pin and a 4 pin)

I should really post pictures

Mustang5L5 · Sep 11, 2021

How are you activating your fuel pump? It’s just a monitor wire. Just needs 12v when the pump is active.

I have the 93 wiring diagrams if that will help. Just needs to wait til the am

BeaverMeat · Sep 11, 2021

Well… after some diagram staring and wire chasing this thing is kittywampus.

The ECU is a 88-92 and allot of the wires match-up. Just not all.

BeaverMeat · Sep 12, 2021

Well… there is no Ford fuel pump relay.

After some more bugged-eyed diagram staring the tan/light green wire from pin 22 is hotwired into the Volvo wiring.

So, yeah. Add 12v to the pink/black wire.

i got confused because the pink/black wire is attached to a green 8-pin pigtail that’s also for the wheel speed sensor

looks like this: (sweet, I cab upload pics on this forum)

BeaverMeat · Nov 14, 2021

Bump!

Completed the surging idle checklist and everything checks-out... still having some slight surging at idle. Much better than before but, it still "shutters" now and then. After some more interwebs I concluded that my code 67 is the problem. Got under the car today and did some harness chasing and lo-and-behold the NSS pigtail is just hanging down the side of the Transmission. There is no female end because it was cut-off at the O2 sensor harness.

Adding a new pigtail and finishing the circuit is the easy part... wiring-up the whole system will be the hard part and will require some Ford to Volvo wizardry.

What will that entail? Do I need to install a switch on the clutch pedal?

NOTE: The engine/trans are from a '90 manual car. No air conditioning (it may have been deleted during the swap. The wiring for the WOT A/C cut-out is there) Also the reverse lights do work.

BeaverMeat · Nov 14, 2021

Found the pigtails in the Motorcraft catalogue.

https://parts.ford.com/content/dam/ford-parts/catalog/sub-category/desktop/Pigtail%20Final.pdf

For the green connector next to the ECU I found WPT-379 (3U2Z-14S411-FSA) "power seat switch connector"

For the NSS male end I will need WPT-361 (3U2Z-14S411-BAA) or WPT-497 (3U2Z-14S411-PYA) "radiator fan control connector"

BeaverMeat · Nov 14, 2021

lol. It must be late because I’m talking to myself…

My bad. The cut wire is for the oil level sensor that was deleted because there is no provision for a light in the Volvo cluster.

evintho · Nov 14, 2021

If you're swapping a Foxy body motor and harness into another vehicle......this is what you need. It identifies and traces every wire/color/connector/circuit/actuator/component/etc in the system. I just swapped a '93 5.0 motor/trans/ECU/harness and the factory FI into a '54 Ford and the factory wiring diagram was invaluable!

1992 Mustang factory wiring diagram

Electrical Fooling the ECU

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