DTC P1398: MISFIRE ADAPTIVE NUMERATOR AT LIMIT Dodge Ram Van B2500

Note. For connector terminal identification, see CONNECTOR IDENTIFICATION . For circuit identification and wiring diagram, see RAM VAN & RAM WAGON wiring diagram in WIRING DIAGRAMS article.

Note. DTC P1398: MISFIRE ADAPTIVE NUMERATOR AT LIMIT is monitored under closed throttle deceleration, with A/C off, engine coolant temperature more than 176°F (80°C) and more than 50 seconds after engine start. Speed at which deceleration occurs must be with vehicle at more than 36 MPH in first gear or 65 MPH in fourth gear. DTC may be stored in Powertrain Control Module (PCM) when PCM senses one of Crankshaft Position (CKP) sensor target windows has more than 2 percent variance from CKP sensor reference window. Possible causes are: improperly installed CKP sensor, defective CKP sensor, defective flywheel, defective crankshaft, defective connectors or defective wiring.

1. Turn ignition on, with engine off. Using scan tool, read DTCs. If DTC SPECIFIC GOOD TRIP COUNTER is displayed and displayed count is "0", go to next step. If DTC SPECIFIC GOOD TRIP COUNTER is not displayed or displayed count is not "0", go to step 5).
2. Ensure ignition is off. Disconnect CKP sensor connector. For CKP sensor location (Схема №21) Visually inspect connector for corroded, damaged, pushed-out or miswired terminals. Repair connector as necessary. Perform TEST VER-5A. If connector is okay, go to next step.
3. Ensure ignition is off. Remove CKP sensor. Inspect flywheel for damage or misalignment. Repair flywheel as necessary. Perform TEST VER-5A. If flywheel is okay, go to next step.
4. At this time, CKP sensor is assumed to be defective. Replace CKP sensor. Perform TEST VER-5A.
5. Turn ignition off. Inspect CKP sensor and connector for damage and proper installation. (Схема №21) Repair connector or replace CKP sensor as necessary. Perform TEST VER-5A. If CKP sensor and connector are okay, go to next step.
6. Turn ignition on, with engine off. Using scan tool in miscellaneous menu, choose CLEAR PCM. Using scan tool, proceed to MISFIRE PRETEST screen. Road test vehicle to perform relearn adaptive numerator procedure. If relearn adaptive numerator procedure is successful, test is complete. If relearn adaptive numerator procedure is not successful, repeat test. Perform TEST VER-5A.