Code P1121 - TPS A RAN

[skibumm100]

Hi guys and gals,

 

More issues with the 98 Leggy GT. Car keeps throwing code P1121 - "TPS A RAN". I was also getting P0122 - "TPS A LOW" but that one doesn't seem to come up anymore. When I start the car it idles OK for a minute then, the idle RPM starts to climb. If I put it in gear the idle drops, then climbs again. Pop it out of gear and the idle jumps to almost 2000 RPM then slowly drops back down to about 900 RPM. If I put it back in gear again it will drop to about 600 RPM. It only does this for a period of time. The rest of the time the car drives pretty normal. I've connected my laptop and OBD II scanner software to it and the TPS seems to work fine. I can watch it on the data screen in real time. I've back-probed the plug on the TPS and the voltage and reference are within spec. The TPS reads zero percent with my foot off the pedal and 100 percent at the mat. The coolant temp sensor is reading fine. I'm tempted to get another TPS out of the junkyard but I don't really see a problem with the one I've got. When I'm backing down the driveway in the morning and it's doing the high idle thing in gear, something will instantly change and it will drive normally. (i.e. you have to hold it back with the brakes but then it snaps out of it and it won't try to push through the brakes)

 

I'm at a loss on this one.

 

Gregg

[Suzam]

I had a bad coolant temp sensor that had similar symptoms but never threw or caused a code. Not sure it that would make the computer throw a TPS code but replacement put the the idle back to normal.

[OB99W]

[...]Car keeps throwing code P1121 - "TPS A RAN". [...] When I start the car it idles OK for a minute then, the idle RPM starts to climb. If I put it in gear the idle drops, then climbs again. Pop it out of gear and the idle jumps to almost 2000 RPM then slowly drops back down to about 900 RPM. If I put it back in gear again it will drop to about 600 RPM.[...]

The code definition you have for P1121 may be misleading you. Codes P1xxx are brand-specific -- it appears that "TPS A RAN" isn't the Subaru code definition. For Subaru, P1121 is "Neutral Position Switch Circuit [High Input, MT Vehicles] [Low Input, AT Vehicles]". It seems your transmission neutral/inhibitor switch isn't making good contact (or connectors/wiring to it are the cause), and therefore the ECU doesn't know whether the car is in gear or not. Check that switch, etc., and you'll likely find the solution.

[skibumm100]

OB99W,

 

Thanks for the reply. I've been out of pocket for a little while but it's time to dig back into this. If I can keep the CEL light off, I plan to get it in the garage to replace the head gasket.....again. It's going on the block after it's running right.