OBD1/OBD2 loom difference

[swiftkid 1]

Right, I've asked this question on VR6OC but thought I'd try here as well. Ever since this post by Mike Edwards I've been curious as to whether it would actually work. I really don't like how the obd2 loom fits, its too long in some places (particularly near the ecu plug) so has to snake round making it very untidy and not OEM how I like it.

 

My question is, what is the differences between a late CP ECU type wiring loom (fusebox to engine bay) and an obd2 one. My MAF and lambda plug is the same, the fan controller and fan is the same, all sensors are the same its only the main plug between the 2 looms that I'm unsure of because of the difference in throttle bodies. By my reckoning, if the 2 looms are the same, a late VR6 (CP ECU) could do an OBD2 in about 3 hours and would literally be a piece of cake as its the wiring that is the scariest bit.

[fla 9]

i've got a few diagrams from ETKA showing the schematics rather than being just 'wiring diags'. there is a lot of extra loomage on the OBD2, and the shape does seem to be a bit different. I'm using them to prepare myself for the swop.

odb2engineloomdiagram1.pdf

[robo22sri 10]

I have a late odb2 golf loom at my mates! will be intresting replies on this thread, subscribed!

[swiftkid 1]

There is a lot of extra loomage on the obd2 but most of it needs cutting out. As far as I know the ONLY difference between my original and the obd2 from sight is the ambient air temp sensor which is part of the aircon system so not needed anyway and the engine loom which definitely needs changing. I just don't know whether the loom contains the same wires because I know it contains the same plugs

[robo22sri 10]

I was speaking to Karl is the throttle positon sensor different on the odb2 to odb1?

[KADVR6 0]

I was speaking to Karl is the throttle positon sensor different on the odb2 to odb1?

 

 

you told me this thread was about the engine loom, and not the loom from the fuse box to the engine bay ya muppet lol

[fla 9]

I think the engine loom (going to the sparks etc from the ecu) is the same.

[Kevin Bacon 5]

Obviously you mean the 'car' harness because you need the throttle body part of the harness for OBD2 if you want to use it or not.

 

There are some differences in how OBD2 is wired up. IIRC the MAF power supply is only there during cranking and engine running and it doesn't need / use an ECU relay. The knock sensor, lambda sensor and crank sensor harness is the same as OBD1 though.

There might also be some internal wiring differences inside the ECU, so it may not be just as simple as swapping a few wires about.

 

Personally I would use the whole ODB2 conversion in it's entirety.

[robo22sri 10]

you told me this thread was about the engine loom, and not the loom from the fuse box to the engine bay ya muppet lol

 

Opps lol sorry you pansy

[VR6Pete 0]

I've managed to get a fairly good fit with my OBD2 stuff now, had a weekend on it, sorted all my wiring issues, pinned everything back and mae it look neat... honestly, you cant tell its not been there all along!

[fla 9]

Obviously you mean the 'car' harness because you need the throttle body part of the harness for OBD2 if you want to use it or not.

 

There are some differences in how OBD2 is wired up. IIRC the MAF power supply is only there during cranking and engine running and it doesn't need / use an ECU relay. The knock sensor, lambda sensor and crank sensor harness is the same as OBD1 though.

There might also be some internal wiring differences inside the ECU, so it may not be just as simple as swapping a few wires about.

 

Personally I would use the whole ODB2 conversion in it's entirety.

 

Ah OK. I've got the OBD2 fusebox with mine too, is it better to swop that over too? Connectors are all still attached. Remember i converted my auto to manual and Nathan mentioned something in his thread about the wiring so thats also a consideration. Thanks for any advice.

[swiftkid 1]

It was just something I was wondering, obviously it would be massively useful for any CP ecu owners to be able to just swap the bolt on parts over because the biggest pain I had was that wiring loom.

 

Another point is that I do hear comments now and again about other wires needing cutting and splicing to do with the fans and I've never quite got a definitive answer. I don't think my fans worked 100% after I did the obd2 conversion but I driven it in about 6 months so can't remember for sure

[fla 9]

Hoping to start the prep on this over the weekend - would someone be kind enough to indicate on the pdf below which parts of the loom can be removed? I dont think anything connects to the Diavia aircon which has a separate loom i think. Much appreciated.

 

In fact if there is a summary of the circuits that need to be removed, that would be great - ie what is not required by the system. Obviously the headlight loom will come into this, but what about the rest? What do the other connectors do?

odb2engineloomdiagram1.pdf

Edited February 27, 2012 by fla
clarification of request

[fla 9]

Has anyone got any pics of the ends of both looms just showing the connectors that go to the relay panel?