Location of Manual Resistor?

[BRGChimaera430]

Evening all,

RoverGauge thinks my car is an Auto, I know it should have a 510 ohm resistor on Pin 34, does anyone know the location of this? I've traced the Orange/Black wire through some of the harness but i'm yet to find the location of the resistor.

Thanks in advance.

[Steve_D]

It will be wrapped in the loom a little way up from the ECU and fuel relays etc.
It will be a standard resistor sealed in a clear plastic sleeve so one of its wires may have fractured.

Steve

[blitzracing]

Crossed wires I think- hes looking for the one for the auto gearbox indication. Assuming its a wrong reading-from memory the Steve Heath ECUmate manual talks about it. Its available as a download if you google it.

[Steve_D]

Steve_D said:

It will be wrapped in the loom a little way up from the ECU and fuel relays etc.
It will be a standard resistor sealed in a clear plastic sleeve so one of its wires may have fractured.

Steve

Just had a quick look at mine. Got its position wrong in my earlier post. If you follow the loom from the ECU it goes up into the base of the dash. If you remove the dash top you should find the loom arriving at 2 large connectors. One is brown to other clear nylon. Just after the clear connector you will find the resistor in the loom. Mine is a normal resistor in black heatshrink.

And for clarity I am referring to the gear select resistor. In my loom the wire from ECU pin 34 is Orange/Black as far as the clear connector but is black the other side of the connector.

Before you go digging I would disconnect the ECU and measure the resistance between pin 34 on the connector and a known good earth.

Steve

[BRGChimaera430]

Thanks guys,
I actually had to remove the centre of the dash too to get to the connector as it was tucked in the cubby hole in the centre console. I'm a bit confused about what the arrangement is, hopefully the picture shows it but there is a capacitor wired in and then one end of the resistor which obviously serves no purpose, I will get a replacement resistor and wire it in but is the capacitor supposed to be there?

Thanks again.

[Steve_D]

No capacitor in mine that I can see. I've not removed the heatshrink but the lump inside it looks to be just the shape of one resistor.

Steve

[blitzracing]

That makes no sense at all- a capacitor is open circuit on a DC circuit like this- the only reason you would have one is if AC noise was a problem - anyway that is a 16k resistor if it was connected? - here in info from the ECUmate manual:

BOX
This signal tells the ECU whether the car is in park or neutral (P/N)
or drive (-D-). This is normally changed by a micro switch on the
automatic gear box. The ECU recognises the gearbox status by
measuring the voltage between the input pin and ground. There
is normally a resistor connected between these two pins and by
changing this, the ECU can discriminate between values and hence
gearbox status. As a result, the values change a little and are not
simply 0 or 255. Instead, the ‘0’ value can actually vary between 0
and 50 and the ‘255’ value from 230 to 255. With sports cars like
TVRs, it can display an intermediate value of about 128 — indicated
by ???. With some Marcos cars, this signal is left open with no
modifications to the software and this can lead to a fault code being
flagged up. The cure is to connect a 510 ohm resistor between the
signal and ground to force it into the P/N mode. The fault can also
happen if the engine is started while in Drive mode as the ECU
interprets this as being a fault. The starter should be disabled when
in this mode. With the TVR version, this does not cause a fault —
but with standard ECUs it can. Changes in the status will cause the
ECU to adjust the revs via the stepper motor position.

Edited by blitzracing on Tuesday 19th June 15:53

[BRGChimaera430]

I had the same thought that it made no sense, i've just gone and double checked and actually I had just rushed tracing the wire through the connector and assumed that resistor / capacitor mess was it, in fact its not.

Wrapped up in insulation tape in the wire next to it is the resistor i was looking for and indeed it is broken through fatigue, and so I will replace that.

While i'm there though i'm now concerned that the circuit on the other wire is definitely not right as the resistor isn't doing anything. I've traced it through and its connected to a yellow wire on Pin 6 of the ECU connector which is listed as speed transducer, any idea what this resistor and capacitor should be doing on this circuit?

Thanks again.

[blitzracing]

Its likely to be signal conditioning of some sort then.

[Steve_D]

blitzracing said:

Its likely to be signal conditioning of some sort then.

I'm not electronic savvy so is that something along the lines of solving the earth potential we discussed a year or more ago?

Steve

[blitzracing]

Its a tiny capacitor- so if its in series it wont let an DC through at all- all you get is a spike on the leading and trailing edge of the square wave the transducer produces- But this does not make sense- when I data logged the speed input to the 14CUX it did not look like a signal passed through a small capacitor. And why a resistor thats open ended ? - it would make more sense to have the resistor in series, and the cap to ground to remove any high frequency noise to ground.

[Steve_D]

blitzracing said:

Its a tiny capacitor- so if its in series it wont let an DC through at all- all you get is a spike on the leading and trailing edge of the square wave the transducer produces- But this does not make sense- when I data logged the speed input to the 14CUX it did not look like a signal passed through a small capacitor. And why a resistor thats open ended ? - it would make more sense to have the resistor in series, and the cap to ground to remove any high frequency noise to ground.

Perhaps the resistor broke and someone fitted the capacitor thinking it was a resistor....its got 2 wires coming out of it so should be fine!!!!!

Steve

[Penelope Stopit]

Steve_D said:

blitzracing said:

Its a tiny capacitor- so if its in series it wont let an DC through at all- all you get is a spike on the leading and trailing edge of the square wave the transducer produces- But this does not make sense- when I data logged the speed input to the 14CUX it did not look like a signal passed through a small capacitor. And why a resistor thats open ended ? - it would make more sense to have the resistor in series, and the cap to ground to remove any high frequency noise to ground.

Perhaps the resistor broke and someone fitted the capacitor thinking it was a resistor....its got 2 wires coming out of it so should be fine!!!!!

Steve

As above, it is obvious that whoever carried out that work was clueless

[BRGChimaera430]

I've ignored the mess on that line for now, i've replaced the gear resistor, and then with RoverGauge found the Throttle Pot was out of range. I'm now getting the idle Mode illuminated in RG so at least its trying to idle, i've got a few other questions/issues now.

1. It only drops the idle to 1000rpm and doesn't try to drop it any further, at this point the stepper motor is still at 17%. Is this normal? I imagined a lower RPM and that it would keep going until the stepper motor was close to closed?

2. I think I may have an air leak, the car smells very rich at idle and the long term trim is adding fuel at 100% on the Even Bank only though? I cant immediately find a leak and why is the trim only on one bank? Does anything in my screen capture support/contradict this?

3. Is there any other readings that look off in my screen capture, this was after having the ECU disconnect and then starting the car from cold and letting it warm up for 10mins before getting long term trim. Ignore the MIL light, there is definitely no codes, the software got confused when I tried to connect with the ignition off.

Thanks again guys.