P0122, P0121

laserman1955 · **Joined:** Sun Jan 13, 2008 7:09 pm **Posts:** 2

1998 Ford Expedition 5.4L 2WD, 175,000 miles, excellent condition. Problem is "High Idle Speed". In gear, running @ 900 RPM. Park @ 1200 RPM. Replaced throttle position sensor. Reference voltage of throttle position sensor is 4.06 V. Scan tool indicates 18% for TP Sensor at idle. Checked throttle body for obstructions. Clean, no problems. Butterfly closing completely. Checked MAF sensor. Found to be OK. Checked IAC valve. Found to be OK. Checked for vacuum leaks. Found none. Can the problem be the PCM? If so, what could cause it to fail? No other codes indicated.

Sponsored Links · **Joined:** 29 Jun 2004 08:12 pm **Posts:** N/A

jpb · **Joined:** Wed Oct 17, 2007 9:29 pm **Posts:** 76

P0121 Throttle position performance problem. P0122 Throttle position circuit low input. Check all related wiring tfor TPS for open and shorted conditions. Double check TPS for proper insallation.

laserman1955 · **Joined:** Sun Jan 13, 2008 7:09 pm **Posts:** 2

Thanks. The TPS install is a no-brainer. Only fits one way. Not like some GM models which require a "preload". I'm sure it installed correctly.

Checked the wiring for opens and shorts. None obvious. I even "wiggled" the wires. The dealer told me it's the PCM. Any way to confirm that?

Webmaster · **Posted:** Mon Mar 10, 2008 4:58 pm

FYI, I've posted an "FAQ" type article on the P0122 code - http://www.obd-codes.com/p0122

jeff compton · **Posted:** Tue Mar 11, 2008 3:58 pm

did you use a tps from FORD?

P0122, P0121

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