Hey Guys, Very new to the site. I have a VL with a standard RB30 engine. A while ago when it was running a bit rough i pulled the coolant temperature sensor (the one that goes to the ecu) off to give it a clean and it fell apart. I couldn't find a replacement so i just placed the wires on the terminals without the plastic plug (they most probably touched). Since then the engine has be running rich and possibly in some sort of limp mode. I think that i have narrowed it down to the ecu. I have tested the resistance on the sensor and it all checks out ok. I have test driven the VL with the wires plugged into the sensor and without them being plugged in and there is no difference in performance. Is it possible to damage the ecu by the two wires from the sensor touching or being placed around the wrong way? Is it possible that a faulty ecu could make it run rich? I have since found a plug but dont know which way around the wires go. There is a brown one and green one. Can someone please help?
It will be on 'enrichment' until it receives a rising temp signal from the coolant. Replace the temp sensor.
Thanks for the reply. Is enrichment like a "limp mode" for these older vehicles? Should i replace the sensor even if it tests out ok? Do you know which way the wires go to the temp sensor or dosent it matter? Thanks in advance.
Enrichment is like using the 'choke', runs richer during cold start. If the temp sensor is faulty(or has a build up of crap over it), the ECU cant tell if the coolant temp is increasing. It will run rich all the time, probably not like 'limp mode', but it wont run efficiently. I sold my VL workshop manuals years ago, which had excellent wiring diagrams, so I'm not sure about the wiring to the sensor....
Thanks for your help Imoengnr, I have replaced the Coolant Temperature Sensor but there is no change. I have also changed over the ecu and 02 sensor but that hasnt helped either. I'm starting to narrow the problem down. I have put a multimeter on the TPS plug (while disconnected from the TPS itself) with the ignition on "ON". One of the pins there is no reading, another just a small reading of about .4 volts and the middle plug is about 11.7 volts (not to dissimilar to direct battery voltage). From what i understand these readings are not correct. I have traced the wire (11.7 one) to the cpu and its reading the same voltage there. i cant find a earth at the same plug either. Any help would be great.
Try and eyeball that section of harness as close as you can. Look for the obvious, like broken wires, but also check for pushed back pins in the harness connectors, you may have an open circuit in one wire.
Update: I decided to trace the wire back to the ECU to find out if there was a problem with it. I pulled the entire loom away from the engine bay and discovered that there was a part of the loom that had been rubbing against something. I pulled away the tape and found at least two wires that were exposed and looked like they had been shorting out. One of them happened to be the blue wire from the TPS harness. There were another three wires that looked a little suspicious, like thay had been rubbing as well. I cut through all of the wire and re-soldered them back together. Unfortunately that has not stopped the problem. It was still coughing at idle and the voltage at the TPS is still about 12 volts. I'm satisfied that it is not shorting any more but i think the shorting of the wires in the past may of damaged the ECU. Does anyone know if this is possible? Hope to get her running well before Christmas day!
Yeah, I tried a different ECU but that was before i found the wiring problem. So there is a chance that the replacement one has been damaged also. Is there some sort of protection in the ECU that would prevent any damage of this type (fuse ect)? Can anyone tell me what the voltage supply to the TPS should read in the VL? Merry Christmas eve.
Another update: I have located the power supply wire for the TPS at the ECU and cut it, turned the ignition to ON and the voltage was still the same as what i find it to be at the harness of the TPS. Could this mean that i have destroyed the ECU or is it putting the vehicle in some sort of limp mode because of a problem which is unrelated? I measured the voltage at the TPS with the harness plugged in with the ignition ON, the top wire (Green) with the throttle at idle reads 7.24 volts with the throttle wide open the volts decrease to 0.07 volts. The middle wire (Blue) with the throttle at idle reads 7.24 volts as you open the throttle wide open it increases to 9.27 volts. Hope this makes sense.
Have you read the fault codes from the flashing LED lights at the ECU? This is always the first step with any diagnosis.
Thanks LeighC, Just ran the diagnostics and the fault code is "23 throttle switch circuit". It appears that one of the wire on the throttle position sensor runs to the automatic ECU (blue/white) maybe this has shorted out and damaged it (as per previous posts). I have check the TPS for resistance and it seems ok. My concern is the voltage at the TPS as per the wire (blue) at the harness. Maybe if these wires crossed over at some stage they damaged the circuit board in either the Automatic Transmission or ECU. Just out of the ECU the Blue wire is reading over 12 volts when isolated. Can anyone conduct a check to see how many volts they get at the TPS harness, with what wires with the ignition turned on, it would be a great help.
