P0120 TPS A Circuit Malfunction
Potential causes of the P0120 code include:
Sticking throttle return spring
MAP or TPS connector corrosion
Misrouted harness causing chafing
Bad TPS
Bad PCM
Possible SolutionsIf you have access to a scan tool, with KOEO (Key on engine off) observe the TPS voltage. With throttle closed, voltage should be about.45 volts. It should gradually sweep upwards to approximately 4.5 to 5 volts as you depress the throttle. Sometimes only a scope can capture an intermittent glitch in the TPS signal voltage. If you notice a glitch in the TPS sweep voltage, replace the TPS.
NOTE: Some TPS sensors require fine adjustment. If you aren't comfortable with using a DVOM (Digital Volt Ohm meter) to adjust the new TPS, then it's best to take the vehicle to a shop. If the voltage is not.45 volts (+or-.3 volts or so) with the throttle closed or if the reading is "stuck" then unplug the TPS connector. With KOEO check for 5 volts reference voltage present at the connector and a good ground. You can check the signal circuit for continuity by jumping a fused wire between the ground circuit of the TPS connector and the signal circuit. If the TPS reading on the scan tool now reads zero, then replace the TPS. However if that doesn't change the reading to zero, then check for an open or a short on the signal wire and if none is found, suspect a bad PCM. If manipulating the TPS wiring harness causes any change in idle, then suspect bad TPS.
P0170 Fuel Trim Malfunction (Bank 1)
Check and test the mass air flow sensor-
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Monday, May 9th, 2011 AT 9:43 PM
