No matter what I do I can`t get rid of codes for sensors. (V8) 1. CTS (coolant temp sensor) voltage high, voltage low, voltage unstable. ACTION TAKEN> replaced with new unit to no avail. 2. TPS (throtle position sensor) TPS stuck, TPS voltage high. ACTION TAKEN> replaced with new unit to no avail. 3. O2 sensor (oxygen sensor) No siginal replaced this as well. to no avail I`ve also replaced my ECU with a fresh unit. What now?, I can`t seem to work it out, I clear them (CODES) try agian and they still come back, it`s f##king anoying, help.
The CTS and TPS share a common wire (should be black w'yellow stripe), either power or earth. Without a car in front of me or a labelled wiring diagram, I don't know which. I suspect it's an earth. That may also explain the O2 sensor and would be a good place to start looking. Try running a jumper wire from each of the PCM earth terminals to an earth on the body, drive the car and see if the codes stop recurring. The O2 sensor earths directly but the two sensors earth through the PCM to the PCM earth wires. That is a diagnostic step, not a fix. The fix would then be to find the earth point and check the earth wire from there back to the PCM terminal. How did you go when you tested the O2 sensor? You should have at least got the 450mV cold signal out of the ECM terminal with the voltmeter black probe earthed on the body. You can also check the other sensor inputs to the ECM in a similar way to the O2 sensor; ignition 'on', dressmaker's pin to the terminal pin at PCM, red test probe terminal to that, black probe terminal to an earth eg. the door hinge pin. Then go to the sensor and check the same colour wire as at the PCM for each (the signal wires) using the dressmaker's pin again to the car wiring terminal with the black probe again going to an earth. The voltmeter will need to be able to read up to 5V DC so set it to 20V DC this time. You should be able to see the TPS voltage change when you move the throttle or accelerator pedal with the ignition on, engine running or off, doesn't matter which, although trying to test WOT may be interesting with it running . The CTS voltage will only change with engine operating temperature so you can connect the meter with engine cold and run the engine up to temp while watching the voltage on the meter.
Thanks, I`ll try that on the weekend, I`m leaning toward maybe even loose wires at the loom connection to the ECU, but either way its safe to say it`s a wiring/earth issue as you explained. cheers again rep point given.
Thanks and no problem. Please post back if you don't understand something that I have tried to describe. The common wire is indeed an earth. On a VP V8 it would go, via the ECM (PCM), to the back of the LHS head, not sure on VR.
K, today I started playing around, firstly the loom has definatly been replaced because none of the colours of wire`s match, though it should be no problem as long as they are going to the right sensor the colour does not matter, second the little manual that came with the multimeter is not very pacific so can someone use windows paint on the pic of the multimeter and tell me what to use in what situation using paint to put arrows and discription`s etc. Feeling like a wiring noob much.:whistling P.S do I use the dressmakers pin to stab the coating of the wire I`m probing like in pic No 2 or what?
hey mate with the multimeter turn it to the one above the one in the pic the 20. then ground the black one and touch the red one to the testing wire. do you have a gregorys? if you do have a look in there it shows you the easiest way to back probe them. it involves pulling the plug out from the ecu and touching the wire. hope that helped
To back probe, leave the connectors attached to the PCM but remove the blue plastic terminal retaining 'combs' (why they are called combs will be obvious when you remove one) that are visible on the wire side of the PCM connectors. That will allow access to the back of the terminals. There is no need to penetrate the wire insulation, just insert the pin (gently) between the wire (terminal) and the plastic PCM connector, from the back of the connector, where the comb tine was. (That is why it's called back probing ). The pin will then make contact with the wire terminal so you can connect to it via the pin to the red meter probe. The way you have the meter set up in the picture will measure up to 2000mV DC (= 2V DC) and will be the best setting to use for the O2 sensor signal. The next setting up, the up to 20V DC range, will be what to use for measuring the rest of the ~0-5 V signals. (The solid horizontal line with the dotted horizontal line underneath it below the 'V' on the top left of the meter indicates the V DC section for the meter dial). The test terminals appear to be in the correct sockets on the meter from what I can see in the picture. The wiring diagram I posted the link to in the thread you posted re. the O2 sensor is for a manual VR V8. I suggested in my earlier post here that you could earth the some of the PCM terminals as a diagnostic test. DO NOT EARTH ANYTHING FROM THE PCM OTHER THAN A BLACK WIRE (Except through the multimeter. The meter will limit the current flow if you are earthing through it).
