| Diagnostic Codes Table | ||
|---|---|---|
| CDL Code | Code Description | Comments |
| 190-8 | Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period | The signal from the primary engine speed/timing sensor is intermittent or the signal has been lost. |
| 342-8 | Secondary Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period | The signal from the secondary engine speed/timing sensor is intermittent or the signal has been lost. |
The engine uses two engine speed/timing sensors. The primary engine speed/timing sensor detects the reference for engine speed and timing from a timing ring with a notched pattern that has been machined onto a portion of the crankshaft gear. The signal from the primary engine speed/timing sensor is also used by the ECM as a control reference during a timing calibration.
The secondary engine speed/timing sensor detects the reference for engine speed and timing from a timing ring with a notched pattern that has been machined onto a portion of the camshaft gear.
The Electronic Control Module (ECM) counts the time between pulses that is created by the sensor as each gear rotates in order to determine rpm. Timing is provided by the unique pattern of notches in the timing ring.
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 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.
A timing offset is determined during each engine start-up. The value of the timing offset is stored in the electronic control module's non-volatile memory until the successful completion of the next engine start-up. If a failure mode for the crankshaft's engine speed/timing sensor is detected during engine start-up, the value of the timing offset that has been stored in memory will be used. This value will continue to be used for the engine's timing calibration until the diagnostic is resolved. A timing calibration cannot be performed manually on this engine.
Both sensors are magnetic sensors. The two sensors are not interchangeable. If a sensor is replaced, a timing calibration is not necessary.
Complete all of the following tasks when you install a speed/timing sensor:
- Ensure that an O-ring is installed on the sensor. If the O-ring is damaged or missing, replace the O-ring.
- Lubricate the O-ring with oil.
- Ensure that the sensor is fully seated into the engine before tightening the bracket bolt.
- Ensure that the electrical connector is latched.
- Ensure that the harness is properly secured, and ensure that each tie-wrap is placed in the correct location.
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| Illustration 1 | g02128717 |
Schematic for the engine speed/timing sensors | |
| Troubleshooting Test Steps | Values | Results |
|---|---|---|
1. Check for Codes A. Connect Cat ET to the service tool connector. B. Check for Active or Logged codes. |
190-8, 342-8 Codes |
Result: Engine rpm is not indicated on Cat ET. Proceed to Test Step 2. Result: There is an active diagnostic code or a logged diagnostic code for an engine speed/timing sensor. Proceed to Test Step 4. |
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| Illustration 2 | g01167684 |
Typical engine speed/timing sensor (1) Mounting flange (2) Mounting surface | |
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| Illustration 3 | g01167704 |
Typical engine speed/timing sensor (3) O-ring | |
| Troubleshooting Test Steps | Values | Results |
|---|---|---|
2. Check the Installation of the Sensor Assembly A. Remove electrical power from the ECM. B. Visually inspect each sensor assembly without removing the sensor assembly from the engine. Ensure that flange (1) is installed squarely against surface (2) . C. Remove the suspect sensor assembly from the engine. D. Ensure that one O-ring (3) is installed on the sensor. Check the O-ring for damage. Replace the O-ring, if necessary. |
Sensor Assembly |
Result: The sensor's components are OK. Repair: Perform the following procedure in order to properly install the sensor assembly: 1. Lubricate the O-ring with engine oil. 2. Fully seat the sensor assembly in the engine. Note: If the sensor assembly will not fully seat into the engine, replace the sensor assembly. 3. Tighten the bracket bolt. 4. Connect the sensor's electrical connectors. Verify that the connectors are latched on both sides. 5. Ensure that the harness is properly secured, and that the tie-wraps are placed in the correct location. Proceed to Test Step 3. Result: At least one of the sensor assembly's components is not OK. Repair: Obtain a new sensor assembly. Refer to the Disassembly and Assembly manual for installation instructions. |
3. Inspect the Electrical Connectors and the Wiring A. Thoroughly inspect connectors. 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 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: 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 completely coupled. Verify that the repair eliminates the problem. If the repair does not resolve the problem, proceed to Test Step 4. |
4. Measure the Sensor Resistance through the Engine Harness A. Disconnect the J2/P2 ECM connectors. B. If you are troubleshooting a problem with the primary engine speed/timing sensor, perform the following procedure: a. Measure the sensor's resistance between P2-25 (primary engine speed/timing +) and P2-35 (primary engine speed/timing -). b. 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 or shake the wires that are directly behind the sensor. Resistance at 25°C (77 °F) (75 to 230 Ohms) C. If you are troubleshooting a problem with the secondary engine speed/timing sensor, perform the following procedure: a. Measure the sensor's resistance between P2-47 (secondary engine speed/timing +) and P2-46 (secondary engine speed/timing -). b. 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 or shake the wires that are directly behind the sensor. Resistance at 25°C (77 °F) (600 to 1800 Ohms) |
Resistance |
Result: The resistance measurement is within the specifications. Repair: Neither a short circuit nor an open circuit is indicated in the circuit. Replace the ECM. Refer to Troubleshooting, "ECM - Replace". If the repair does not resolve the problem, 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 sensor's connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect". C. Measure the sensor's resistance between terminals 1 and 2. Resistance for primary engine speed/timing sensor at 25 °C (77 °F) (75 to 230 Ohms) Resistance for secondary engine speed/timing sensor at 25 °C (77 °F) (600 to 1800 Ohms) |
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: 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. Repair: Replace the speed/timing sensor. Refer to the Disassembly and Assembly for installation instructions. Verify that the repair eliminates the problem. |