Code 138 Throttle Position Does Not Agree With Map
NOTE:
For component terminal identification, see TERMINAL IDENTIFICATION
in this article. For appropriate WIRING DIAGRAMS, see WIRING DIAGRAMS
section.
- Using MUT II scan tool, perform SENSOR READ TEST No. 12 (IAC position). If IAC motor step value increases when A/C switch is turned on, perform throttle body minimum airflow check, go to step 3). If IAC motor step value does not increase, disconnect IAC motor connector. Measure resistance between IAC motor terminal No. 1 and 4 and between No. 2 and 3.
- If resistance is not 38-52 ohms at 68°F (20°C), replace IAC motor. If resistance is 38-52 ohms at 68°F (20°C), check IAC motor control circuit. See CODE 25: IDLE AIR CONTROL (IAC) MOTOR CIRCUIT .
- Start and warm engine until coolant temperature is 176°F (80°C) or more. Turn engine off. Disconnect PCV valve hose from intake manifold. Connect Air Metering Fitting (MB995050) to intake manifold. Disconnect 3/16" idle purge line from throttle body. Cap throttle body nipple.
- Start engine and idle for at least 1 minute with all accessories off. Using scan tool, access SENSOR READ TEST "Minimum Airflow Idle Speed" screen. After test selection, IAC motor will close, idle air spark advance will be fixed and scan tool will display engine speed. Idle speed should be 600-1200 RPM.
- If idle speed is above specification, check IAC motor operation with scan tool. If IAC motor is okay, replace throttle body. If idle speed is below specification, remove and clean throttle body. Reinstall throttle body and repeat minimum airflow check.