Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Complex EFi issue

I need a very specific bit of info if possible.

I’m still having the occasional cutting out at idle problem. 3.9 EFI 14CUX ecu. I’ve tried 3 idle stepper motors, two MAFs, changed the fuel temp sender and cleaned and tested the speedo transducer.

Rover gauge just shows two problems, stepper motor and a mysterious error 69 neutral gear selector switch. Apparently this is a black/orange wire with a resistor on a manual car. Obviously mine is manual.

Where on earth is the wire and resistor? I can see it coming out of the ecu loom to disappear into thin air. So of anyone can point me in the right direction I’d be grateful. No really sure what it does either.

Cheers

Without wanting to sound like a smart-arse .... isn't the gearbox a good place to start? ..... if it's a manual then that's where it's going to know it's in neutral.


K

if only life was that simple eh?

apparently on an auto its connected to the gear selector mechanism but on a manual the wiring connects to earth via a 510 ohm resistor somewhere. I've had a look around the box and gear sticks housing and cant see an appropriate wire or resistor.

apparently (again sorry) on a manual it needs the resistor to fool the ecu into thinking the car is in gear! so the ecu doesn't attempt to adjust the idle via the stepper motor.

I dont know this for a fact but it's just what I've read on other forums (fora?)

cheers

Right ... so it's not a neutral indicator ... just a way of getting rid of an unwanted neutral indicator 🙂

If you start to lose the will to live chasing it you could always cut the black/orange near the ecu and earth it direct throught a 510 ohm resistor off ebay .... eliminate the lost section whilst still fooling the ecu.

K

I seem to remember Lorne (GoMoG.com) when opening up the loom while tracing a wiring fault discovered a whole group of resistors that were in circuit with each of the fuel injectors...!
As for the fault..From a dull memory, I think that turned out to be a screw point protruding through a section and entering the wiring harness, ? My guess is that the resistor in question could be anywhere that was found convenient at the time.. It is a Morgan after all...

more homework has revealed more mysteries. The resistor in located inside the loom on Range Rovers and Discoveries somewhere behind the dash.

one suggestion is as suggested above - cut the wire and connect it to earth using a new known resistor. Another is to measure the resistance through the wire to earth. Both have potential flaws. the resistor could be upstream of the cut, if its gone open circuit it won't help at all, an intermittent break may not show in a static test.

Anyway - I'm going to try both later today and see what I can find out, resistors ordered.

slight update for those that haven't lost the will to live.

I can't locate the resistor but having disconnected the ECU and located the orange/black wire at the ECU connector end I get a reading close to zero ohms on a DVM. This must mean that there is either a direct to earth connection or the resistor has failed as short circuit.

Given that every failed resistor I've encountered before this one has failed open circuit I con only assume there is no resistor or there's a short to earth in the circuit. As I've ordered 5 x 510 ohm resistors I intend to cut the wire and make my own connection to earth via the resistor

Now I'm wondering if there's another orange/black wire for something else - unlikely I think

I tend to be grumpy too and I don`t have much patience for this kind of stuff.

My logic, flawed or otherwise is that the resistor provides an input to the ECU to effect a fuelling solution designed to operate in an auto box situation while stopped at road junctions/ at traffic lights etc, where the auto box may be left in gear, drivers foot on the brake the engine idling, fuelling requirement is different from that which might be required if neutral had been selected due to the reduction on drag/loading of the gearbox internals ..?

It seems we may be looking at a single input..which provides a permanent predetermined resistance to earth on a manual box installation where the ECU has programming designed for an auto box...? If that is the case then why not have the resistor somewhere convenient to the ECU`s terminal, what would be the point of extending the wire to some distant location...?

If you have identified the wire, the terminal and the task the resistor is presumed to perform, and that instead it seems the input terminal is being provided with a short to earth as opposed to 50 ohms, then assuming no damage has been done... hopefully removing the short and installing a resistor might just provide a solution to your issue...... Or Not..!

Just thinking in type and claiming ZERO expertise.

George .... in an ideal world they would have had a dedicated ecu for both types of gearbox ..... my guess is the loom wasn't custom made either and when doing the 'conversion' they just found a spot on the loom where the black/orange broke out of the wrapping (probably for a connector) and spliced the resistor in at that convenient (and out of sight as 'bodges' go) location .... it's what I would have done. Just a guess though.

K

Having spent several hours researching last night I now believe that this orange/black input has three functions. On an auto it provides a straight to earth (0v) solution which in conjunction with the road speed sensor tells the car when it’s come to a stand still and to raise the idle by 100rpm if in neutral or leave lower if in drive to avoid gearbox drag. On a manual it’s supposed to prevent ‘confusion’ by using the resistor to tie pin 34 to 5V thus telling the ecu not to adjust the idle speed.

It’s just possible that with pin 34 floating it will attempt to change the idle speed by opening the stepper motor and cause a stall.

So testing the road speed sensor is on the cards today.