0123238 JOHNSON HOUSING,Upper

Table 1
Diagnostic Codes Table
Description Conditions which Generate this Code System Response
1491-3 Right Turbo Turbine Inlet Temperature Sensor voltage above normal The ECM detects a duty cycle that is greater than 96 percent for ten seconds. The code is logged.
If the signal from the other exhaust temperature sensor is OK, the signal from that sensor is used. If the signal from the other exhaust temperature sensor is not OK, a default value of 0 °C (32 °F) is used.
1491-4 Right Turbo Turbine Inlet Temperature Sensor voltage below normal The ECM detects a duty cycle that is less than 4 percent for ten seconds.
1491-8 Right Turbo Turbine Inlet Temperature Sensor abnormal frequency, pulse width, or period The ECM detects a sensor frequency that is greater than 600 Hz or less than 400 Hz.
1492-3 Left Turbo Turbine Inlet Temperature Sensor voltage above normal The ECM detects a duty cycle that is greater than 96 percent for ten seconds. The code is logged.
If the signal from the other exhaust temperature sensor is OK, the signal from that sensor is used. If the signal from the other exhaust temperature sensor is not OK, a default value of 0 °C (32 °F) is used.
1492-4 Left Turbo Turbine Inlet Temperature Sensor voltage below normal The ECM detects a duty cycle that is less than 4 percent for ten seconds.
1492-8 Left Turbo Turbine Inlet Temperature Sensor abnormal frequency, pulse width, or period The ECM detects a sensor frequency that is greater than 600 Hz or less than 400 Hz. System OperationUse this procedure to troubleshoot any suspect problems with the sensor for the left turbocharger turbine inlet temperature or the right turbocharger turbine inlet temperature.The Pulse Width Modulated Sensor (PWM) provides a signal to the engine's ECM. The PWM signal is used to represent certain engine operating conditions. The sensors receive 8.0 0.4 VDC from a regulated power supply.The ECM performs an automatic calibration of these sensors whenever the ECM is powered and the engine has been off for at least five seconds.The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.The following components can cause problems with the power supply:
Electrical connector or wiring
Sensor
ECMThe most likely cause of a problem is a problem with an electrical connector or wiring. The least likely cause is a problem with the ECM.
Illustration 1 g01534113
Schematic of the PWM sensors for the sensor signal circuit
Illustration 2 g01534075
Location of the connectors that are for the PWM sensor circuit (top side engine view)
(1) Sensor for the right turbocharger turbine inlet temperature
(2) Sensor for the left turbocharger turbine inlet temperature
(3) Right rail connector
(4) Left rail connector
(5) J1/P1 ECM connector
(6) J2/P2 ECM connector
Illustration 3 g01279964
Terminal locations at the P1 ECM connector that are for the sensors for the turbocharger turbine inlet temperature
(P1-5) Digital return
(P1-18) Digital return
Illustration 4 g01279871
Terminal locations at the P2 ECM connector that are for the sensors for the turbocharger turbine inlet temperature
(P2-29) Digital supply
(P2-65) Left turbocharger turbine inlet temperature
(P2-73) Right turbocharger turbine inlet temperature
(P2-92) Digital return
Illustration 5 g01826777
Terminal locations at the left rail connector that are for the sensors for the turbocharger turbine inlet temperature
(Terminal 49) Left turbocharger turbine inlet temperature
(Terminal 63) Digital supply
(Terminal 69) Digital return
Illustration 6 g01534394
Terminal locations at the right rail connector that are for the sensors for the turbocharger turbine inlet temperature
(Terminal 49) Right turbocharger turbine inlet temperature
(Terminal 63) Digital supply
(Terminal 69) Digital return
Illustration 7 g01240891
Sensor connector
(Terminal 1) Sensor supply
(Terminal 2) Sensor return
(Terminal 3) Signal Test Step 1. Check for an "Active" Diagnostic Code
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Determine if a diagnostic code has occurred several times. Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal.
Look for one or more of the following diagnostic codes that are active or logged:
1491-03
1491-04
1491-08
1492-03
1492-04
1492-08Expected Result:No diagnostic code is active for the exhaust temperature sensors.Results:
OK - No diagnostic codes are active.Repair: There may be an intermittent problem in the harness or in a connector. If an intermittent