Loom damage and its effects

Last update:

08/19/2005

Vehicle

Ultima 2.9 24V Saloon

Year

All

Mileage

Any

Repair Cost

£ 4 figure

Repair Part(s)

Engine Wiring Loom

A number of owners have reported strange behaviour from their automatic gearboxes. Symptoms have included

OD flashing
Rough gear shifts
Jumping in and out of drive

The first thoughts were of possible problems with the Gearbox itself however these have been proven to be tough and reliable in the form of the A4LD and the addition of the electronic control systems (that makes it the 'E' version) under the control of the EEC-V computer makes the owner suspicious that this may be a possible cause.

Further investigation of two 24V cars found what was firstly the cause of there particular problems but also what may be a weak link on all 24V Scorpios and all owners should check their cars asap. The damage occurs down between the left bank of cylinders (when viewed from the front of the car - the black loom can be seen in the photograph. It appears that the loom chafes against a plastic clip or metal support and over time causes the insulation to be stripped away revealing bare wires. As these cables communicate signals back to the EEC-V - any damage is going to have devastating effects.

This was noticed by the owners of the vehicles in question in the form of Gearbox problems with gear changes and flashing dashboard lights. As removal of the Scorpio gearbox is going to take a Ford Dealer approximately 10 hours - finding a problem here is obviously your first check before considering other possible problems.

As a continuation of this theme, other 24V owners have experienced the same symptoms but tracked the problem down to a small water leak that occurred between the two bank of cylinder heads (see Water Leaks). The small leak dripped onto the wiring loom that runs between the heads and damage occurred through water penetration - antifreeze is not very nice to electrical connections.

Over time a complete section of the loom rotted and necessitated complete replacement. It should be possible to easily remove the inlet manifolds and plenum chambers to gain access to this area to cure the water leak but as you can see from the article, leaving it for too long will result in an expensive repair. If your 24V leaks small amounts of water on a regular basis then check this area as soon as possible.

Wiring loom damage between the heads

Damage caused by a water leak between the
cylinder heads - see Water Leaks

When damaged, the wiring loom causes problems with shifting and flashing OD light and it is difficult to diagnose - even Ford Main Dealers have shown not to be misled by problems in this area until they have exhausted all other possibilities. Replacing the loom requires the gearbox to be dropped and is expensive in labour costs even though the loom itself is not too expensive. However be careful - main dealers have supplied the wrong looms on more than one occasion.

You may suspect the loom when there are Diagnostic Trouble Codes obtained from the EECV Powertrain Control Module, either by paying for diagnostic from a Main Dealer or using your own Lead and you obtain:-

	More than one DTC reporting a failed or missing sensor
	A code that clears itself (Genuine faults remain until repaired)
	Multiple unconnected DTCs reporting different sensors
	Errors that multiply after rain or washing the car, or clear as the car becomes dry.

If you find yourself in this situation and your vehicle was built before June 1996 we recommend that you examine the wiring looms in the engine bay. It will be of Arnitel and some insulation on the thin-walled control wires will have cracked in situ making the conductors prone to poor connection and/or damp. Post 6/96 cars are wired with Raychem44 and have presented no problems to date.

EricR