Is the only computer controling the engine and trans in my 1985 xj6 the ecu or ecm

 

Just one, the "ECU" in the trunk. It controls the fuel injection only

Cheers
DD

 

The ECU in the Series 3 XJs is an analogue electronic device that controls the fuel injection.It has no computing circuits, memories, or programs. Ignition is by the usual distributor and coil except that the points are replaced by a reluctor device and small amplifer to provide the pulse to the coil. There is a single wire from one of the coil connections to the ECU so the injector pulses can be timed correctly.This is the only link between the two. The ECU is a very reliable device and most injection faults are caused by the sensors that feed signals to it.