ECU pinout/wiring diagrams ???

[apw30534]

I've got a 2007 VP 8.1 Gi-H in my boat.

I also have a 8.1GXi ECU and harness from a similar year boat, sitting on my workbench. Both ECU's interchange with the boat harness, but the GXi ECU will only start and run the engine for a few seconds, then shuts down.

I'd like to compare harness wire colors/pinouts to confirm compatibility or troubleshoot a bad ECU.

Any thoughts on where I might locate such a thing ? I've searched all morning and came up empty handed.

Thanks in advance.

 

[alldodge]

Hey @muc can you advise?

 

[muc]

Hey @muc can you advise?

Sure, just go to.

Manuals & Handbooks | Volvo Penta

Workshop manuals, owners manuals and service protocols for your engine. Get your manual and service protocol here.

www.volvopenta.com

And input the serial number.
This information is usually found in the diagnostic manual, and/or the wiring diagram manual.

 

[alldodge]

Sure, just go to.

Manuals & Handbooks | Volvo Penta

Workshop manuals, owners manuals and service protocols for your engine. Get your manual and service protocol here.

www.volvopenta.com

And input the serial number.
This information is usually found in the diagnostic manual, and/or the wiring diagram manual.

Was thinking you might know if there were any pin out differences and just mention those. OP would know his serial number but probably not the other harness. Looks like way more complex I guess, each serial number could be different

 

[apw30534]

Was thinking you might know if there were any pin out differences and just mention those. OP would know his serial number but probably not the other harness. Looks like way more complex I guess, each serial number could be different

Yeah this is my concern. I have the serial number from my boat engine and have both ECU's and both harnesses, but no practical way to compare them and no absolute confirmation of the model year on the loose harness/ECU package. They are both the same ECU plugs and both are drive by wire, but that doesnt narrow things down very much. lol

 

[muc]

Was thinking you might know if there were any pin out differences and just mention those. OP would know his serial number but probably not the other harness. Looks like way more complex I guess, each serial number could be different

Yes can get very complex. Sometimes the only way is to talk to Volvo tech support. I do know that just because 2 ECMs look the same doesn’t mean they will have the same pin outs.
I have had brand new engines that exhibited this same symptom. I found that 2 of the pins in the ECM plug were reversed. I assumed that somehow the wrong harness got installed on those engines and slipped through manufacture/boat builder testing. In most cases the manufacturer would want to have me replace the complete harness under warranty. in those situations the dealer holds the harness for 90 days in case the manufacturer wants them back. When they don’t call it back we are supposed to destroy it. But sometimes an enterprising parts person/warranty administrator will sell them on the used market. Same kind of goes with used ECMs. How do they get on the used market? Was it a freeze damaged engine that got replaced complete? Or was it a ECM that sank or maybe damaged by a voltage spike and isn’t repairable? Buyer beware on the used market, there’s a reason that nobody will take a return on them.

 

[apw30534]

Yes can get very complex. Sometimes the only way is to talk to Volvo tech support. I do know that just because 2 ECMs look the same doesn’t mean they will have the same pin outs.
I have had brand new engines that exhibited this same symptom. I found that 2 of the pins in the ECM plug were reversed. I assumed that somehow the wrong harness got installed on those engines and slipped through manufacture/boat builder testing. In most cases the manufacturer would want to have me replace the complete harness under warranty. in those situations the dealer holds the harness for 90 days in case the manufacturer wants them back. When they don’t call it back we are supposed to destroy it. But sometimes an enterprising parts person/warranty administrator will sell them on the used market. Same kind of goes with used ECMs. How do they get on the used market? Was it a freeze damaged engine that got replaced complete? Or was it a ECM that sank or maybe damaged by a voltage spike and isn’t repairable? Buyer beware on the used market, there’s a reason that nobody will take a return on them.

The spare ECU and harness came from a reputable guy and apparently was a complete running (but worn out) 8.1GXi. No idea what boat it came from. (It could be for a Sea Ray or a Cobalt... and completely incompatible with my Chaparral.) He rebuilt the engine for his Chevy pickup and sold me the harness/ECU package. I was hoping I could plug the ECU into my boat, swap the cam and drill a hole in the throttle body blade... and have the HO version of my 8.1. Was trying to keep things simple and somewhat "factory appearing"... without the steep learning curve of an aftermarket ECU/ignition control package. It's obviously very possible that the ECU is smoked or the pinout is for a completely different brand of boat.
Either way, I found the correct (#7746659) VP manual for my boat, confirmed by the serial number and have it ordered... so I will get it figured out one way or another.

 

[alldodge]

Do you have a scanner, and was there any codes?
Might help to narrow it down

Assume they are both mechanical shift and not DTS

I'm looking at Merc just to maybe get some clues if they did something different

Another thought, wonder if Bob at OBD Diagnostics might help. He does repair and does have a few Gi and GXI for sale. My guess is he would have some good info if available

 

[apw30534]

Do you have a scanner, and was there any codes?
Might help to narrow it down

Assume they are both mechanical shift and not DTS

I'm looking at Merc just to maybe get some clues if they did something different

Another thought, wonder if Bob at OBD Diagnostics might help. He does repair and does have a few Gi and GXI for sale. My guess is he would have some good info if available

No scanner as of yet... but that is on my to-do list.

I did contact Bob awhile ago about my current ECU and he said he doesn't (or cant) do anything with these EGC ECU's.

In hindsight... my life would have been much easier if I had just purchased a Merc powered boat instead. The aftermarket support for Volvo Penta is pretty much non-existent... and every time I go down this road, it leads me to an aftermarket ECU package.

 

[alldodge]

In hindsight... my life would have been much easier if I had just purchased a Merc powered boat instead. The aftermarket support for Volvo Penta is pretty much non-existent... and every time I go down this road, it leads me to an aftermarket ECU package.

Same here that's why I stay clear also

 

[apw30534]

I ordered some Volvo Penta manuals and wiring diagrams.
Interesting stuff.
What I find most interesting is pin #25 and pin #26 on my ECU... Apparently the ECU gets a separate signal directly from the tach.
I find it odd that it uses a tach signal when it already has cam and crank sensor inputs (which drive the tach)... and appears that it only throws a code if they are shorted, not when they are open... so if those wires were cut, the ECU would not know how fast the engine is spinning... yet the tach would still function ?

 

[muc]

I ordered some Volvo Penta manuals and wiring diagrams.
Interesting stuff.
What I find most interesting is pin #25 and pin #26 on my ECU... Apparently the ECU gets a separate signal directly from the tach.
I find it odd that it uses a tach signal when it already has cam and crank sensor inputs (which drive the tach)... and appears that it only throws a code if they are shorted, not when they are open... so if those wires were cut, the ECU would not know how fast the engine is spinning... yet the tach would still function ?

Do you have any wires connected to pins #25 and #26? Based on the screenshots you posted, these pins aren’t used in this application. I’m just guessing here about those pins. But that circuit is probably there to provide the option for cruise control.

The last 2 screenshots deal with the tach output. This is a single wire that goes to the tachometer. It’s monitored for shorts to ground and positive because those 2 failure modes might affect some of the other circuits in the ECM. In this application it isn’t monitored for an open because that won’t affect anything other then a tach that doesn’t work and you’ll be able to see that without a scanner.

I highly recommend you get Diacom. When you order this from Rinda, tell them you have a Volvo and they will usually include some of the service literature and that might have a copy of the school handbook we get in class that will help you understand how this system works.

 

[apw30534]

Do you have any wires connected to pins #25 and #26? Based on the screenshots you posted, these pins aren’t used in this application. I’m just guessing here about those pins. But that circuit is probably there to provide the option for cruise control.

The last 2 screenshots deal with the tach output. This is a single wire that goes to the tachometer. It’s monitored for shorts to ground and positive because those 2 failure modes might affect some of the other circuits in the ECM. In this application it isn’t monitored for an open because that won’t affect anything other then a tach that doesn’t work and you’ll be able to see that without a scanner.

I highly recommend you get Diacom. When you order this from Rinda, tell them you have a Volvo and they will usually include some of the service literature and that might have a copy of the school handbook we get in class that will help you understand how this system works.

Pin #58 is "tach output" which is where it throws me off... as this should be the signal telling the tach needle where to point.
Pins #25 and #26 are "speed pos and neg" which I *think* is voltage returning to the ECU from the tach. Only reason I think this is because of the statement in the very last screenshot that says:
"The ECM monitors the amount of voltage coming from the tachometer and sets DTC 2618 (or 2619) if the voltage is outside the set parameters"

I will hop in the boat tonight and confirm wires or not on those two pins.

And yes... I think it's time to buy Diacom software and better familiarize myself with the system while everything still works properly and before I have a failure of some kind, like the knock sensor in that other recent thread. Do you sell this software by chance ?

This is what I have:

 

[apw30534]

This is the GXI ECM: (I dont have a serial number to go with it)

 

[apw30534]

This is the GI ECM in my boat:

 

[muc]

Volvo tech support can decode those ECM #s.

"The ECM monitors the amount of voltage coming from the tachometer and sets DTC 2618 (or 2619) if the voltage is outside the set parameters"

That's kind of a typo in the manual. It isn't there in later manuals. It doesn't really monitor voltage except for shorts to ground or positive. We use a Hz meter when troubleshooting this wire.