Skylark L4-144 2.4L DOHC VIN T SFI (1997)
-
Damaged MAP sensor seal. Refer to MAP Sensor (VIN K).
-
Damaged fuel injector 0-rings. Refer to Fuel Injector.
-
Damaged gasket at the throttle body, intake manifold, PCV valve cover, EGR pipes, or EGR valve mounting surface.
-
Incorrectly installed or malfunctioning PCV valve. Refer to Positive Crankcase Ventilation Valve.
^
Damaged or sticking throttle plate or IAC valve. A throttle plate or IAC valve that allows too much airflow with the throttle closed may cause a high
idle and DTC P0121 to set. Refer to Idle Air Control System Check for diagnosis.
^
Incorrect 3X reference signal. A condition that causes an incorrect 3X reference signal may cause the MAP sensor value to stop updating. This
condition can cause DTC P0121 to be set during a closed throttle condition. An incorrect 3X reference signal should cause DTC P1374 to be set. If
DTC P1374 and DTC P0121 are set, diagnose DTC P1374 first.
^
Stuck open EGR valve. An EGR valve stuck partially open may cause the TP sensor low test to fail and DTC P0121 to set. A sticking EGR valve
should cause DTC P1406 to set. If DTC P1406 and DTC P0121 are set, diagnose DTC P1406 first.
^
Restricted exhaust system. Refer to Restricted Exhaust System Check
^
Skewed MAP signal or malfunctioning MAP sensor. An incorrect MAP signal may cause the PCM to incorrectly calculate the predicted TP sensor
value during high engine load or closed throttle situations. Check for the following conditions:
-
an unusually low MAP reading with the key ON, engine not running.
-
an unusually high MAP reading at idle. Either condition can cause DTC P0121 to set.
^
Poor connection at the PCM. Inspect harness connectors for the following conditions
-
Backed out terminals.
-
Improper mating
-
Broken locks.
-
Improperly formed or damaged terminals.
-
Poor terminal to wire connection.
^
Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the ECT display on the scan tool while moving
connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the malfunction.
If DTC P0121 cannot be duplicated, the information included in the Fail Records data can be useful in determining vehicle mileage since the DTC was
last set. If the DTC occurs intermittently, performing the DTC P1122 or DTC P1121 Diagnostic Charts may isolate the cause of the malfunction.
