DTC 121

Possible Causes

• •TPS 1 calculated percentage is 20% or more lower than TPS 2
• •Throttle is out of specification
• •Problem with the TPS signal circuit
• •Intermittent Problem
• •TPS1 or TPS2 signal shorted to ground in harness
• •Faulty ECM connection
• •Faulty ECM
• •Faulty harness

Suggested Actions

1. 1Perform On-Board (OBD) System Check.
2. 2With Key ON, Engine Off, and System Mode set to 'Stopped', enable 'DBW Test' mode and slowly depress FPP sensor (or type desired throttle opening % in the TPS Command box on the DBW page to sweep throttle on stationary applications) to check for TPS1 and TPS2 calibration differences.
3. 3With Key Off, disconnect throttle from harness, then with Key ON, Engine Off, and System Mode set to 'Stopped', enable 'DBW Test' mode and check if the voltage for both TPS1 and TPS2 is <0.100 VDC.
4. 4Connect TPS1 signal to the 5V reference at throttle connector while observing TPS 1 voltage, repeat for TPS2, and check if DST displays both TPS1 and TPS2 voltage over 4.90 VDC.
5. 5With Key Off, disconnect wire harness header from ECM, carefully remove yellow lock from header at device output terminal, and check if resistance is <5 ohms between MAP input at ECM header and signal at device (probe on the side of the terminal to avoid spreading pins).

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