Electrical Fooling the ECU

Mustang5L5

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Mod Dude
Feb 18, 2001
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How much of the OeM harness do you have?

Really you just need to tie the clutch and trans switch in parallel and replicate what is in post #6
 
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BeaverMeat

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I have everything except for the interior stuff. I don’t have the harness that plugs into the green 8-pin from the ECU. There is a few wires that have been cut-off from the black and grey 8-pin connectors under the hood. Everything on the ECC onward is still there.

All the ignition related stuff is cross-wired into the Volvo harness. There is no clutch safety so it must be by-passed somewhere because it starts.

Forgot about post #6. I’ll take an other look at the wiring.
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
36,820
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Massachusetts
Essentially you are grounding pin 30 through the two switches in parallel to pin 46. This is also assuming you are using a manual trans A9L ECU. You can create this wiring pretty easily but I would recommend adding the clutch switch to the pedal box.


The other plug location on the above switch is for the starter circuit. If aren't using a starter interrupt you can cut one of the wires that activates the starter relay and tie it into the clutch switch here giving you a clutch safety.
 
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BeaverMeat

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The car has a cruise control switch on the clutch pedal already. The circuit opens when the clutch is depressed preventing the engagement of the cruise. I may tie into that circuit with a relay or something. When the clutch switch opens it closes the relay and tells the ECC “hey, buddy! You’re in neutral now”

How does the Ford unit work? Does the clutch have to be fully depressed for it to engage?
 

BeaverMeat

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3F4E53B6-CB0A-4DA9-8EB7-D310C01AD612.jpeg
7916AC16-2BD2-48CD-A47A-A6BC4543D54B.jpeg
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
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Massachusetts
So those are connectors C403 and C201. These connectors connect the main eec harness to the dash harness. (There’s another one down by the ECU - green plug) Unfortunately my manaal doesn’t tell me which is which.


Pin 30 passes through c201 on a light blue/yellow wire. I think I see it on the black connector. You can test continuity back to pin 30 on the ECU to see if it’s it
2CBDCFD6-6921-42A0-90F4-D78EAED3CC9B.jpeg
 

BeaverMeat

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The green one is unplugged. I have a pigtail for it so I can connect the fuel pump secondary circuit to the Volvo pump relay. I haven’t figured out what the other wires do yet.

Thankfully only one end of the black and grey connectors are cut off. It’s a bit of a mess. Some go through the connector then go back through the same harness again and are spliced into a Volvo connector

Thanks.

Also. The grey/red wire is the “ground”?
 

BeaverMeat

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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
F5CFDAC1-9649-4984-8DE5-E15F8A3AEE4C.jpeg
8217A0A9-AF67-462F-A5D0-3ED5F0936640.jpeg

According to this schematic the Black/white ground goes to grey/yellow at connector C212
 

Mustang5L5

Put lubricant all over the balls
Mod Dude
Feb 18, 2001
36,820
12,748
224
Massachusetts
According to this schematic the Black/white ground goes to grey/yellow at connector C212

Not necessarily ground. Your just making continuity between pin 46 and 30 on a manual transmission car.


Automatic would be different as pin 30 will see actual power during crank/start. That’s why using manual ecus with automatic wiring will fry the ECU
 
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