C15 and C18 Engines for Caterpillar Built Machines Caterpillar

Use this procedure to troubleshoot problems with the engine speed/timing sensors. This procedure covers the following diagnostic codes:

Table 1

Diagnostic Codes Table
CDL Code	Code Description	Comments
190-8	Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period	The code is logged. , The Electronic Control Module (ECM) will default to the secondary engine speed/timing sensor, when a valid signal is not received from the primary engine speed/timing sensor. The engine will shut down only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are abnormal.
261-11	Engine Timing Offset fault	The code is latched in the active state until the power to the ECM is cycled. The offset for timing calibration is set to zero while the diagnostic code is active.
342-8	Secondary Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period	The code is logged. If a valid signal is not received from the secondary engine speed/timing sensor, the ECM will default to the primary engine speed/timing sensor. The engine will shut down only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are 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 Engine 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 the 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. Also, 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 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	g03015640
Schematic for the engine speed/timing sensors

Table 2

1. Determine the Diagnostic Code A. Establish communication between the Cat ET and the ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Start the engine. Run the engine until the engine is at normal operating temperature. If the engine will not start, monitor the engine rpm on Cat ET while the engine is being cranked. Cat ET will need to be powered from another battery while the engine is being cranked, if battery voltage is low. C. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 30 seconds so that any codes may become active. D. Look for these codes on Cat ET: · 190-8 · 342-8 · 261-11	Diagnostic code	Result: Engine rpm is not indicated on Cat ET. Proceed to Test Step 2. Result: There is an active or a logged 190-08 or 342-8 diagnostic code. Proceed to Test Step 4. Result: There is an active or a logged 261-11 diagnostic code. The wires from one of the engine speed/timing sensors are connected to the wrong terminals on the P2 connector. Repair the wiring. Verify that the problem is resolved. Result: There is not an active or a logged diagnostic code. Refer to the appropriate symptoms in Troubleshooting, "Symptom Troubleshooting".
2. Check the Installation of the Sensor Assembly A. Turn the keyswitch to the OFF position. B. Visually inspect the sensor assembly without removing the sensor assembly from the engine. The flange must be flush against engine in order to ensure proper operation. Inspect the bracket. Verify that the bracket allows the flanges to be flush against the engine. Verify that the bracket is not bent. If the bracket is bent or if an obstruction is preventing the sensor assembly from being installed correctly, the engine will not start. C. Remove the sensor assembly from the engine. D. Ensure that one O-ring is installed on each sensor. Check the O-rings for damage. Replace the O-rings, if necessary	Sensor installation	Result: The sensor assembly components are OK. Perform the following procedure in order to install the sensor assembly: · Lubricate each O-ring with engine oil. · Fully seat the sensor assembly in the engine. If the sensor assembly will not fully seat into the engine, replace the sensor assembly. · Tighten the bracket bolt. · Connect the sensors electrical connectors. Verify that the connectors are latched on both sides. · Ensure that the harness is properly secured, and that the tie-wraps are placed in the correct location. Proceed to Test Step 3. Result: The sensor assembly components are not OK. Obtain a new sensor assembly. Perform the following procedure in order to install the sensor assembly: · Lubricate each O-ring with engine oil. · Fully seat the sensor assembly in the engine. If the sensor assembly will not fully seat into the engine, replace the sensor assembly. · Tighten the bracket bolt. · Connect the sensors electrical connectors. Verify that the connectors are latched on both sides. · Ensure that the harness is properly secured, and that the tie-wraps are placed in the correct location. Verify that the problem is resolved.
3. Inspect the Electrical Connectors and the Wiring A. Thoroughly inspect the connectors for the ECM and sensors. Refer to Troubleshooting, "Electrical Connectors - Inspect". B. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the engine speed/timing sensors. C. Check the torque of the allen head screws for the ECM connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values. D. Check the harness and the wiring for abrasion and for pinch points from each sensor back to the ECM.	Electrical connectors and wiring	Result: The harness and connectors appear to be OK. Proceed to Test Step 4. Result: The connectors and/or wiring are not OK. Repair the wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the repair eliminates the problem.
4. Measure the Sensor Resistance through the Engine Harness A. Disconnect the J2/P2 ECM connector. B. If you are troubleshooting a problem with the primary engine speed/timing sensor, perform the following procedure: 1. Measure the sensors resistance between P2-25 (Primary engine speed/timing +) and P2-35 (Primary engine speed/timing -). 2. Check for an intermittent open circuit or for a short circuit by moving the harness while you take the resistance measurement. Pull the wires that are directly behind the sensor and shake the wires that are directly behind the sensor. The resistance should measure between 75 and 230 ohms. C. If you are troubleshooting a problem with the secondary engine speed/timing sensor, perform the following procedure: 1. Measure the sensors resistance between P2-47 (Secondary engine speed/timing +) and P2-46 (Secondary engine speed/timing -). 2. Check for an intermittent open circuit or for a short circuit by moving the harness while you take the resistance measurement. Pull the wires that are directly behind the sensor and shake the wires that are directly behind the sensor. The resistance should measure between 600 and 1800 ohms.	Sensor resistance	Result: The resistance measurement is within the specifications. A short circuit or an open circuit is not indicated. Perform the following procedure: · Temporarily install a new ECM. Refer to Troubleshooting, " ECM - Replace". · Start the engine. Run the engine until the engine is at normal operating temperature. · If the problem is resolved with the test ECM, connect the original ECM and verify that the problem recurs. · If the problem returns with the original ECM, replace the ECM. Verify that the problem is resolved. Result: The readings are not within the specifications. The sensor resistance is not within the acceptable range when the sensor resistance is measured through the engine harness. Proceed to Test Step 5.
5. Measure the Resistance of the Sensor A. Disconnect the harness connector for the suspect sensor. B. Thoroughly inspect the sensors connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect". C. Measure the sensors resistance between terminals A and B. For the primary engine speed/timing sensor, the resistance measurement should be between 75 and 230 ohms. For the secondary engine speed/timing sensor, the resistance measurement should be between 600 and 1800 ohms.	Sensor resistance	Result: The reading is within the specification. There is a problem with the wiring between the engine speed/timing sensor and the ECM. There may be a problem with a connector. Repair the wiring and/or the connector. Replace parts, if necessary. Verify that the problem is resolved. Result: The reading is not within the specification. There is an electrical problem with the engine speed/timing sensor. Perform the following procedure in order to check and install the new sensor assembly: · Before you install the new sensor assembly, measure the resistance of the new sensors. If the resistance measurements of the new sensors are within the specifications, install the new sensor assembly in the engine according to the following procedure: · Loosen the bolt and remove the bolt that holds the sensor assembly to the engine. · Ensure that O-rings are installed on the new sensor assembly. Verify that the O-rings are free of damage · Seat the sensor assembly and tighten the bolt. · Ensure that the harness is secured in the proper location. Verify that the problem is resolved.

Complete the procedure in the order in which the steps are listed.

If the procedure corrected the issue, return the engine to service.

If the procedure did not correct the issue, Contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).