This is a very long and confusing problem. I will try to make it make sense:

The check engine light in my car is on for the full range throttle sensor. I checked the resistances in the sensor and they are a little off but not enough to be causing the light to come on. I disconected the 6 pin connector from the ECU and checked the voltages. The 6 pin connector is arranged with 3 pins for the full range sensor and 3 pins for the narrow range sensor. The 3 pins are a constant + and a constant - coming from the ECU, and a variable voltage that returns the throttle position to the ECU. For the narrow range sensor the voltages are correct, 5V for the + pin, 0V for the - and variable pin. The full range, however, reads 5V for both the + and variable pins and 0V for the negative. Because the variable pin returns a voltage from the tps to the ecu there should not be voltage in it with the throttle sensor disconected,correct? I think this is what is making the check engine light go on.



Why?? Is the ECU bad or is it a problem with the wiring harness? The current has to either be coming across wires in the harness or leaking backwards out of the ECUs throttle sensor input.



The car really jolts at low RPMs and idles rough so i would like to fix this problem.

A couple other things. When i touch the + probe of the voltmeter to the variable pin, the one that isn't working, something inside the engine bay clicks. It sounds like it might be a solenoid valve but i'm not sure. Also, I checked the check engine codes 3 times since i got my car about 3 months ago, each about a month apart. The first time i checked i got codes for the full TPS and 2 solenoid valves. the second time the tps and 4 solenoid valves, the third time the tps and 5 solenoid valves. Either the whole solenoid system is falling apart or the ECU is slowly dying, probably the second.



One last question. If i do need to replace the ECU, which looks likely, should i go with an aftermarket instead of stock. What is a good yet afordable aftermarket ECU?



Thanks

 

the check engine light mean there either and open, short or its out of range (most dont have a range, the tps does though). the ecu's do seem to vary a bit on what is the right range. the solenoids all share the same branched 12v power. its possible you have a harness problem, the ecu's are usually pretty durable. the tps might just be bad, its common



mike

 

I don't think the TPS is bad though because the TPS isn't even hooked up when i'm getting these readings. It probably is the wiring harness then.

Thanks

 

the tps needs the 5v signal to output right



mike

 

The tps is powered by 5V coming FROM the ECU. It returns a voltage between 0 and 5V TO the ECU. With the TPS disconnected the return voltage should be 0. . . it is 5.

 

harness, those should be 2 seperate wires



mike