The following is from the service site:

2002 > G 1.5 SOHC > Fuel System
[ P0121/P0122/P0123 ]DTC[/align]

Diagnostic item[/align]

P0121[/align]TPS Circuit Range/Performance Problem[/align]

P0122[/align]TPS Circuit Low Input[/align]

P0123[/align]TPS Circuit High Input[/align]

DESCRIPTION

[/align]The Throttle Position sensor mounts on the side of the throttle body and is connected to the throttle valve shaft. The TPS is a variable resistor (potentiometer) whose resistance changes according to throttle valve shaft position. During acceleration, the TPS resistance decreases; during deceleration, the TPS resistance increases.

[/align]The Engine Control Module (ECM) applies a reference voltage to the TPS and then measures the voltage that is present on the TPS signal circuit. The ECM uses the TPS signal to adjust timing and injector pulse width. The TPS signal along with the MAF sensor signal is used by the ECM to calculate engine load.[/align]

FAILURE CONDITIONS

[/align]The ECM will set P0121 and the Malfunction Indicator Lamp (MIL) will turn on if the engine load indicated by the Throttle Position (TP) sensor and the MAP sensor are different. This code indicates that the throttle position and air flow readings by the TPS and MAP sensor, or ECM, do not result in the expected engine load value.

[/align]The ECM will set P0122 and the Malfunction Indicator Lamp (MIL) will turn on if the throttle angle is reported as less than 2.1 degrees for more than 0.2 seconds during 2-driving cycles. This code indicates an unusually low throttle position angle being read by the TP sensor or ECM.

[/align]The ECM will set P0123 and the Malfunction Indicator Lamp (MIL) will turn on if the throttle angle is reported as greater than 105.4 degrees for 0.2 seconds during 2-driving cycles. This code indicates an unusually high throttle position angle being read by the TP sensor or ECM.[/align]

Code P0121 indicates the MASS airflow sensor and the TPS are not in agreement as to how much air is flowing into the engine as a result of a problem with the TPS. If the MASS AFS was malfunctioning, it should give the P0106/107/108 series of error codes. I suppose they are saying that since neither a P0122 or 123 code was found, that the TPS was operating correctly and the MASS AFS is at fault. I guess time will tell now.

 

Thanks for all you help.

When the last post mentions a code 121 comes on if the MAP and tps are different, and then at the bottom it says code 121 comes on when the MASS afs and tps are different, do they mean the same thing. Are the MAP and MASS af related? I am guessing that for their to be no engine light on, the MAP the MAFS and the TPS have to agree.If the tps is ok but the MASS is not then, does the MASS change the MAP until the MASS is fixed, or could their be something wrong with the MAP as well.

Is the MASS afs the connection located between the tps and the air filter?
If it is and I unplugged it, and that is the problem, would the problem go away, not that I would leave it like that, but it could be useful info.

The car definately did not run as well on my way home last night, maybe because it was cooler. It doesn't like when I slow down without the brake and then re-speed up without stopping, like cruising to a stop light, getting down to 10 mph and then reaccelerating without ever stopping.

 

MAP (although I think that's an aboration of MAF), MAF (Mass Air Flow), MASS sensor are refer to the Mass Airflow Sensor. Yes, it's mounted on the intake between the air filter box and the throttle body on the manifold intake. On some cars, it's mounted on the side of the filter box. You cannot run the engine with this sensor unplugged. That will generate another set of error codes, and the engine will run rough as well. You might try cleaning the probe on the inside. The aftermarket additive market has several vendors that make aerosol Mass Airflow Sensor cleaners. You simply disconnect the sensor body (the tube) from the intake and spray away. I've seldom heard of any good come from this procedure, particularly if you've maintain the air filters and changed them on a routine basis. Cleaning the MAF seems to be required more often with K&N style filters that need to be washed and then treated with a light oil to work properly. I guess folks apply too much of the oil spray to the filter and the excess contaminates the probe. However, the MAF is probably the most expensive sensor to replace on the engine, so most folks try the cleaner first. If you do this, be sure to have the sensor hooked back up before you start the engine. I guess I'm puzzled as to why one of the MAF error codes hasn't surfaced if the problem is truly with this device.

 

well, I went back to the place where I got my oil done and asked them if they would recheck my codes, which they did.121 came up, and I asked if there were any other codes, they said "no". I said "are you sure" and sure enough 172 System too rich bank 1. So I guess whatever is wrong is upsetting the O2 sensor, or the O2 sensor craped out. Is the tps upsetting the O2 because it is properly working but adjusting to something that isn't? Does thiscode help at all?

 

It means the oxygen sensors need to be replaced, but before I'd do that, I think I'd try to have someone else pull the error codes. I have little faith in "quicky lube" outfits knowing how to properly change oil much less provide other services.

 

I was watching the screen and saw the codes myself. I should have known they might have missed one the first time.