Overdrive / Cruise Control / Speedo issues..

[MSF]

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[Dongskie2]

Its the OD Solenoid. Replace it.

[nj swb]

I think you're on the right path with the coolant sensor, but I'm not sure earthing it is necessarily a definitive test. Do you have any information about the sensor and its characteristics? Is it one wire or two?

If it's a negative temperature coefficient device then resistance will decrease as temp increases, so the ECU is probably looking for a resistance below a certain value - but shorting it may be interpreted as a defective sensor.

If it's a positive coefficient device then resistance will increase with temp, so a short will be seen as a cold temperature.

In an older vehicle, a sensor problem could be a wiring problem - an intermittent short in the wiring loom, a break in a wire making intermittent contact, or a dirty connection with variable resistance. Such problems can be painful to trace.

If your sensor is single wire, then the electrical connection of the sensor body to the engine or engine to chassis could also be affecting the reading that the ECU sees - try "cracking" the sensor and retightening it, and use a multimeter to check for voltage between the body of the sensor and your battery negative terminal.

[brw0513]

Was your diagnostic scan using the flashing check engine light or some electronic scan tool?

I ask because I have a Throttle Position Sensor error according to the CEL flashing code that is reported as a Speed Sensor error by a mate's scan tool.

Are the gear changes a bit clunky at all? That could be a sign of a TPS error apparently.

[Just Cruzin]

My NL throws the TPS error code, cruise control still works just doesn't like slowing down when you use the coast button. Will hold whatever speed you first set, but when you release the coast button will revert to the initial speed set.

[EDMOND]

On the off chance that it's a negative temperature coefficient contraption, by then square will decrease as temp increments, so the ECU is clearly seeking after down an impediment underneath a specific respect - yet shorting it might be translated as a defective sensor.

[brw0513]

Hi MSF.

You could try a local MM dealer to see if they would help you out by reading your ECU codes with a genuine MUTIII reader.

I lucked out with my local MM dealer one Friday afternoon. The young mechanic was more than willing to help me out.

Worth asking.

[DWC]

To save any more confusion, the O/D sensor is a normally open temp switch. It closes at around 50deg C grounding the wire from the transmission control unit which enables O/D. That is why grounding that wire works independent of the sensor. If you used thread tape when you put the new sensor in it may have insulated the threads and not worked as it should. The AT light could indicate a faulty TPS.
With the cruise control, disconnect the wiring to the vacuum unit on the passenger near the fuse box. The motor is connected to terminals 1(pos blue/orange) and 4(neg red/black). Connect to 12V. Its only a small motor so not very loud but you should see the throttle cable moving if it's working. If that's good it could be the controller under the dash. Hope this helps.
Cheers