CAT 3126B Fault Code: 22-11 PID: Flash Code 42 SPN: 637 FMI: 11 Primary to Secondary Engine Speed Signal Calibration

The Engine Control Module (ECM) detects the following conditions:

•The primary speed/timing sensor and the secondary speed/timing sensor are off by more than three degrees.
•A timing calibration has been successfully completed.
•The battery voltage is above 9 V.

The engine uses two engine speed/timing sensors. Both of the engine speed/timing sensors detect the reference for engine speed and timing from a unique pattern on the camshaft gear. The Engine Control Module (ECM) counts the time between pulses that is created by the sensor as the gear rotates in order to determine rpm. The ECM remembers the pattern of the pulses. The ECM uses the pattern of the pulses in order to determine the position of the crankshaft.

When the timing has been established, the ECM triggers each injector in the correct firing order at the correct time.

The actual timing and duration of each injection is based on engine rpm and on load. If the engine is running and the signal from one of the camshaft position sensors is lost, no noticeable change in engine performance will be noticed.

The engine will start and the engine will run when only one sensor signal is present from either of the sensors. The loss of the signal from both of the sensors during engine operation will result in the termination of injection and the shutting down the engine by the ECM. The loss of the signal from both of the sensors during start-up will prevent the engine from starting.

Both sensors are magnetic sensors. The two sensors are not interchangeable. Do not switch the positions of the sensors. The two sensors must be replaced as a pair. If the sensors are replaced, a timing calibration is not necessary for the engine. Timing calibration is only necessary after replacing an ECM that will not communicate.

Probable Causes:

1) ECM Connection
2) Engine speed sensor failure or installed improperly
3) Engine speed sensor harness
4) ECM Failure