21860001 Volvo.Penta Idler gear

expected position of the camshaft is incorrect or the polarity of the wiring to a speed/timing sensor is reversed. System Response:The Electronic Control Module (ECM) will log the diagnostic code.The ECM sets engine timing calibration to zero degrees.
The engine may misfire.
The engine may experience low power and/or reduced speed.
The engine may experience increased exhaust emissions and/or white exhaust smoke.Test Step 1. Check the Installation of the Speed/Timing Sensors
Visually inspect the sensors for correct installation:
Ensure that the sensor's mounting flanges are fully seated onto the surface of the engine.
Ensure that the locating notch on the flange of each sensor is oriented correctly.
Ensure that the sensor's brackets are not bent or broken. Ensure that the brackets are securely holding the sensor in place.
Ensure that the sensors are tight in the housing bore. If a sensor is loose in the bore, check the condition of the sensor's O-ring seals. Ensure that the seals are not missing. Also, inspect the seals for damage.
Check for the correct installation of the sensor's connectors. Ensure that the electrical connector is securely latched. Check for the correct polarity in the wiring at each sensor connector and at the ECM connector.
Ensure that the harness is properly secured, and ensure that each tie-wrap is placed in the correct location.Expected Result:The sensors, the connectors, and the wiring are correctly installed.Results:
OK - The sensors and the harness are OK. The problem is not with the sensor or the harness. There may be a mechanical problem with the engine's front gear train. Proceed to Test Step 2.
Not OK - A problem has been identified with the installation of the sensors and/or the harness.Repair: Correct the problem that has been identified. Replace parts, if necessary. Ensure that the diagnostic code is no longer active.A timing calibration is necessary after this diagnostic code has become active. Refer to the diagnostic functional test Troubleshooting, "Engine Speed/Timing Sensor - Calibrate".STOPTest Step 2. Check the Condition of the Engine's Front Gear TrainThe problem may be due to the incorrect orientation of the camshaft gear with respect to the orientation of the crankshaft gear during engine operation. Check the front gear train for damage and excessive wear:Refer to Disassembly and Assembly.
Remove the cover from the front gear housing.
Check for correct timing between the crankshaft gear and the camshaft gear.
Check the gear train for gear tooth failure.
Check the gear train for excessive gear tooth wear. Perform a timing gear backlash check.
Check each idler gear assembly for excessive wear to the bearing and/or the idler stub shaft. Check for correct bearing clearance.Expected Result:The mechanical condition of the gear train is within specifications.Results:
OK - The condition of the gear train is OK.Repair: The problem is not in the gear train. Clear the diagnostic code. Refer to the diagnostic functional test Troubleshooting, "Engine Speed/Timing Sensor Circuit - Test"..STOP
Not OK - The mechanical condition of the gear train is not within specifications.Repair: A problem with the gear train has been identified. Make the necessary repairs to the gear train. Clear the diagnostic code. A timing calibration is necessary after this diagnostic code has become active. Refer to the calibration procedure Troubleshooting, "Engine Speed/Timing Sensor - Calibrate".Verify that the original problem has been resolved.STOP