This is my first post but it has me scratching my head. I've searched but didnt realy get the results I was looking for. Im still searching now.

I've been dealing with this 2001 Chevy Malibu LS V6 for a few months now and Im stumped. The OBDII is throwing a DTC P0122 Throttle Position Sensor Low input. The car will free rev to about 2500 rpm on startup and accelerate on its own. This has almost caused 3 wrecks so far and the car is in need of brake pad replacement because of the uncontrolled acceleration. The problem was intermitent and becoming more frequent. Did some looking into it and several things pointed towards the TPS.

The TPS was bad. The rotator portion of the sensor was VERRY loose and wobbley, so I replaced the TPS. The connector on the harnes side was corroded and loose so I replaced that as well. I put on a new sealing boot and coated the connector with electrolitic grease to prevent corrosion and bad contacts. The problem seemed to be fixed because it didnt act up for a month.

Now the SES light is popping on and off with the P0122 again and the car is back to its old BS again. I was looking into how to relearn the ECM's TPS settings but havnt found those procedures yet. Im at a dead end so any professional or learned opinion is greatly appreciated.

Thanks for any help I can get

Mike

 

you problem could be the voltage going to the sensor is not right i belive it should be 5 volts (not a 100% sure on your car) and if the sensor is not getting the right voltage the sensor will not work correctly

 

that is true. your reference voltage is going to be 5v going to the sensor. you may getting a reading on a DMM ranging from 4.56 volts to 5.2 volts. that is a good range and means that it is getting the correct voltage. if the sensor is not getting the right voltage, the sensor will not work properly no matter how many times you replace. the part that sends the voltage to that sensor is going to be the ground side on the ECU. check all your grounds and make sure they are good. if you have a Digital Mutlimeter check the voltage before and after the ECU and at the sensor. if you are getting 5v before the computer and not after something is wrong with the computer. have the computer checked at that point and you may or may not have to replace it depending on the results you get.

i hope this helps.

 

Glad someone else out there had more onfo than me i just remember reading in the hanes book about it for my truck and was kinda hoping it was the same

 

Sorry been real busy at work and havnt had a chance to do too much. Here is what I found. Measured with a DMM the 5V refrence channel is putting out 4.98V (essentialy 5). The low revrence has 0 volts. Here is the interesting part. Ground to 5V ref has no continuity, which you would expect being a hot wire going into the sensor. The <1V line has continuity to ground.

It's looking like the <1V circuit has grounded out to a chassis ground some where down the line. there is suposed to be a small charge on there but there is nothing. Still scratching my head.

 

tesing the tps with a dvom is pretty straight forward. One wire is 5v, one is ground, and the center wire is your reference wire that goes to the ecm. If you measure voltage on the center wire, (one lead to ground, one to the center wire), and move the throttle smoothly through the motion of the accelerator, you should have a smooth change in voltage without spikes, or erratic reading. It is much better to do this with an analog meter but we all don't have access to this. WOT should be around 5v and I believe closed throttle is about .8v

 

Yeah it is pretty straight forward but the problem I ran into the refrence wire is at 0v and when the power is off or on has continuity to ground. Tested the leads and the refrence lead is grounded out side of the sensor. So in sumary... TPS=Good, TPS Wiring = BAD!

Im thinking the grounding out of the low refrence is whats throwing the p0122.

 

that would definitely be whats causing the problem. if the sensor is good but cant send the signal back to the ECU it will pull a code. leading to whatever sensor the computer "thinks" is bad. remember you are dealing with a computer and even computers have their faults and will not be specific

 

trace that wire back to a splicein the engine compartment. Various sensors use the same source of 5v. There should be a splice in one of the wire looms

 

I have had the same problem as Mike has with my Malibu. But I have a twist to it, I got the tps fixed & the idle & acceleration is fine now. But the new problem is I can drive the car for a little bit & it goes dead while going down the road. What could this be?
My problems started with an overheating problem. Once that was fixed then my accelerating problem began & come to find out it was a cracked head that caused all of my problem as far as the accelerating & idle. I have been dealing with my problem for 1.5 yrs.
My question is could this be an electrical problem for my car to just go dead as driving down the road?
Could it be the fuel pump going bad? or the fuel pump just not performing correctly?
Leslie