C7 and C9 Industrial Engines Caterpillar

• Primary engine speed/timing sensor

• Secondary engine speed/timing sensor

This procedure covers the following diagnostic codes:

• 190-08 Engine Speed abnormal

• 342-08 Secondary Engine Speed signal abnormal

The engine uses two engine speed/timing sensors. Both sensors detect the reference for engine speed and timing from a unique pattern on the camshaft gear. The Electronic Control Module (ECM) uses the pattern of the pulses in order to determine the position of the crankshaft. The ECM measures the time between the pulses that are created by the sensors as the gears rotate in order to determine rpm.

Under normal operation, the secondary engine speed/timing sensor is used to determine timing for starting purposes. The secondary engine speed/timing sensor is used to determine when the piston in the No. 1 cylinder is at the top of the compression stroke. When the timing has been established, the primary engine speed/timing sensor is then used to determine engine speed.

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 sensor is lost, no noticeable change in engine performance will be noticed. If the engine is running and the signals from both sensors are lost, fuel injection will be terminated and the engine will be shut down by the ECM.

The engine will start when only one sensor signal is present. The engine will not start if the signals from both sensors are lost.

Both sensors are magnetic sensors. The two sensors are not interchangeable. Do not switch the positions of the sensors. Replace the sensors as a set. If the sensors are replaced, a timing calibration is not necessary.

If a replacement of the ECM is required, the ECM parameters and the timing calibration can be transferred from the suspect ECM to the replacement ECM. Timing calibration will not be necessary. This feature requires the Caterpillar Electronic Technician (ET) and this feature is only possible if the existing ECM can communicate with Cat ET. Use the "Copy Configuration - ECM Replacement" feature on Cat ET.

Complete all of the following tasks when you install the speed/timing sensors:

• Ensure that an O-ring is installed on each sensor. If an O-ring is damaged or missing, replace the O-ring.

• Lubricate the O-rings with oil.

• Ensure that the sensor assembly is fully seated into the engine before tightening the bracket bolt.

• Ensure that each electrical connector is latched on both sides.

• Ensure that the harness is properly secured, and ensure that each tie-wrap is placed in the correct location.

Illustration 1	g01120211
Schematic for the engine speed/timing sensors

Illustration 2	g01120250
Left side view (1) Engine (2) Flanges (3) Bracket

Illustration 3	g01142633
Sensor assembly (4) O-ring

Illustration 4	g01120293
Left side view (1) P400 connector for engine timing calibration (2) J2/P2 connectors (3) J401/P401 connectors for the primary engine speed/timing sensor (4) J402/P402 connectors for the secondary engine speed/timing sensor

Illustration 5	g01099116
P2 terminations for the engine speed/timing sensors (P2-25) Primary engine speed/timing − (P2-26) TDC probe + (P2-35) Primary engine speed/timing + (P2-36) TDC probe − (P2-46) Secondary engine speed/timing + (P2-47) Secondary engine speed/timing −