I'm trying to trace an earth output (pin 52) from the ECM to the throttle motor relay in the engine fusebox. I'm having trouble finding the exact direction of the harness. The wires from the ECM travel right on the rear of the engine but the wires from the relay travel down in front of the bumper, around the inside of the wheel arch and through the bulkhead so any ideas? I'm looking for a break in the wire as there is an open circuit from pin 52 to the relay. According to the wiring diagrams this wire also goes through a 42 way connector, also on the rear of the engine but it isn't there? This connector is known as PI41 42-WAY / BLACK / ENGINE HARNESS TO VEHICLE HARNESSES.

My car is late 2003 and the wiring diagrams are May 2002, so my question is, does the wiring change after the facelift ?

Any help would be very much appreciated.

 

Other cars have had problems with corroded wires in harness(es) which run in the front bumper and one or other front wheel arches (not sure which), including the STR used long-term by EVO magazine.

In case you want extra info, GTR (via jag web site) www.jaguartechinfo.com may have it but you have to register and later pay.

You could run a separate wire short-term but from where to where will be a challenge I guess.

 

Thanks for the reply and advice.

I took the bumper off this morning but there is no noticeable corrosion although there was some water inside the harness, the continuity of the wire in question was also there with a resistance of up to 0.2 ohms. The only other place to check now is the left hand wheel arch. To say that I'm p*ssed off would be an understatement. It's even more confusing as the output wire from the ECM is in the harness that goes over the rear of the engine, I'll have to further check the path that this wire eventually takes.

I'm aware that there could be other issues with the car but this wire is showing no life at all with an open circuit from the ECM to the relay, so in this case there's no way at all that the throttle body motor can work.

 

An update.

Managed to trace the green/red wire from pin 52 of the ECM which is supposed to, when activated, earth and energise the coil on the throttle motor relay. The wire, as mentioned before, is part of the engine harness that is right at the back of the engine. The wire goes to the

Quote:

16-WAY / GREY / ENGINE HARNESS TO TRANSMISSION HARNESS

and is looped back through as a yellow wire which goes to pin 23 of the ECM plug although the 2002.5 wiring diagram says that pin 23 is a white/green wire, but it isn't it's yellow !!!

The maintenance disc that we all use says to remove the ECM plug and check the continuity between the throttle relay base and pin 52 of the plug....this is always going to be open circuit though if the pin 52 green/red wire is routed behind the engine and comes back as a yellow wire into pin 23.

 

If the diagram's wrong or for extra details, the only place I know to look for an update would be the GTR site I posted. I take it you checked that the connector at the PCM matches the kind shown on about p23 of the diagrams (described as Engine Control Module, under the part Control Module Identification).

 

Thanks for the reply.

Yes, the wiring diagrams for the throttle body to the ECM are definitely wrong. I now suspect that the problem lies with the ECM, I must do some further testing before I can confirm this though.

I'll be completely waterproofing the wiring loom behind the bumper as I may as well do it as the bumper is still off the car. I'll wrap the loom with pvc tape, then some split flexible conduit then either more pvc tape or maybe even some self-amalgamating tape.