0174741 JOHNSON THROTTLE FRICTION CONTROL

Table 1
Diagnostic Trouble Codes
J1939 Code and Description Comments
190-8
Engine Speed Sensor : Abnormal Frequency, Pulse Width, or Period The code is logged. The Electronic Control Module (ECM) can default to the secondary engine speed/timing sensor. The default will occur if a valid signal is not received from the primary engine speed/timing sensor. The engine will shutdown only if the signals from the primary engine speed/timing sensor and the secondary engine speed/timing sensor are abnormal.
723-8
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 shutdown 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 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. The primary engine speed/timing sensor is then used to determine engine speed and the signal from the secondary camshaft sensor is ignored.After locating the No. 1 cylinder, the ECM triggers each injector in the correct firing order and at the correct unit injector timing. The actual timing and duration of each injection is based on engine rpm and load. If the engine is running and the signal from the primary engine speed/timing sensor is lost, a slight change in engine performance will be noticed. The change will be noticed when the ECM performs the changeover to the secondary engine speed/timing sensor. Loss of the signal from the secondary engine speed/timing sensor during engine operation will not result in any noticeable change in engine performance. However, if the signal from the secondary engine speed/timing sensor is not present during start-up the following conditions may exist:
The engine may require a slightly longer amount of time to start up.
The engine may run rough for a few seconds until the ECM determines the proper firing order by using the primary engine speed/timing sensor only.The engine will start and the engine will run when only one sensor signal is present from either of the sensors. Loosing the signal from both of the sensors during engine operation will result in the termination of injection. The ECM will then shutdown the engine. The loss of the signal from both of the sensors during start-up will prevent the engine from starting.Both sensors are magnetic sensors with an integral connector. The two sensors are not interchangeable. Do not switch the positions of the sensor. If the sensors are replaced, a timing calibration is not necessary for the engine.
Illustration 1 g03683458
Schematic for the engine speed/timing sensors
Complete the procedure in the order in which the steps are listed.
Table 2
Troubleshooting Test Steps Values Results
1. Check the Engine Speed/Timing Circuit
A. Connect Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Turn the keyswitch to the ON position.
C. Monitor the "Engine Starting" screen in Cat ET
D. Start the engine and run the engine. The problem may occur when the engine is at any operating temperature. However, the problem is more likely to occur when the engine is at the normal operating temperature.
Circuit Check
Result: The engine started.
Proceed to Test Step 2.
Result: The engine did not start.
Proceed to Test Step 3.
2. Check for Diagnostic Codes
A. While the engine is running monitor Cat ET for diagnostic codes. Also monitor the "Engine Starting" screen for an engine speed/timing that is "Not Detected".
B. Wait at least 30 seconds for activation of the diagnostic codes. Look for these codes on Cat ET:
190-8
723-8
Diagnostic Codes
Result: There is an active diagnostic code or there is a timing pattern that is "Not Detected".
Proceed to Test Step 5.
Result: There is not an active diagnostic code and there is not a timing pattern that is "Not Detected".
Repair: Download the "Warranty Report" from the engine ECM. Troubleshoot any diagnostic codes that may be present.
Return the unit to service.
3. Check the Battery Voltage
A. Monitor the "Engine Starting" screen in Cat ET.
B. Monitor the battery voltage. Crank the engine for 5 seconds.
Battery Voltage
Result: The battery voltage is OK.
Proceed to Test Step 4.
Result: The battery voltage is not OK.
Repair: Refer to Troubleshooting, "Engine Cranks but Does Not Start".
4. Check the Engine Speed and the Engine Speed/Timing Status
A. Monitor the "Engine Starting" screen in Cat ET.
B. Crank the engine for 5 seconds. While the engine is cranking, verify that the sensors show an acceptable cranking speed.
C. While the engine is cranking check the status of the engine speed/timing.
Speed/Timing Status
Result: The sensors show an acceptable cranking speed. The timing pattern shows "Detected".
Repair: Refer to Troubleshooting, "Engine Cranks but Does Not Start".
Result: A sensor does not show an acceptable cranking speed and/or the timing pattern shows "Not Detected".
Proceed to Test Step 5.
Illustration 2 g02227733
Typical left side engine view
(1) Crankshaft speed/timing sensor
Illustration 3 g02227753
(2) Camshaft speed/timing sensor
Table 3
Troubleshooting Test Steps Values Results
5. Inspect the Sensor Assembly
A. Turn the keyswitch to the OFF position.
B. Visually inspect the sensor and the sensor assembly without removing the sensor assembly from the engine. Flanges (2) must be flush against the surface of the front timing gear housing (1) in order to ensure proper operation.
C. Inspect bracket (3). Verify that the bracket securely holds the flanges of the sensors flu