Each month in Diagnose This! we present a real-life service scenario with clues as to what the ultimate diagnosis was. If you think you know the answer, be the first to e-mail Dsmith@rrpub.com with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.

Vehicle: 2000 Peterbilt Model 379
Key components: Cummins N14 engine with Celect Plus fuel system
Scenario: This truck stumbles, experiences low power, the “stop engine” warning light comes on at times and there is no communication with the scan tool.
Clues: INSITE error code 5402 indicates that there is a date-link fault between the data-link adaptor and the engine ECM. The J1587 data link pinpoint tests OK, as per specification at the engine-mounted, 6-pin Deutsch connector.

Vehicle: 2000 Peterbilt Model 379
Key components: Cummins N14 engine with Celect Plus fuel system
Scenario: This truck stumbles, experiences low power, the “stop engine” warning light comes on at times and there is no communication with the scan tool.
Clues: INSITE error code 5402 indicates that there is a date-link fault between the data-link adaptor and the engine ECM. The J1587 data link pinpoint tests OK, as per specification at the engine-mounted, 6-pin Deutsch connector.

Vehicle: 2005 Sterling
Key components: Mercedes OM926LA engine with exhaust gas recirculation (EGR), Allison automatic transmission
Scenario: The driver complained of oil pouring out of the exhaust manifold on cold startup. The photo shows what the driver saw, and there was a 6-inch diameter puddle of oil on the floor upon startup.
Clues: Power appears OK, smoke emissions were greater than normal, but not severe, and cleared as the engine warmed. Fluid levels are OK and there are no fault codes in memory.

Each month in Diagnose This! we present a real-life service scenario with clues as to what the ultimate diagnosis was. If you think you know the answer, be the first to e-mail Dsmith@rrpub.com with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.

Vehicle: 2005 Sterling
Key components: Mercedes OM926LA engine with exhaust gas recirculation (EGR), Allison automatic transmission
Scenario: The driver complained of oil pouring out of the exhaust manifold on cold startup. The photo shows what the driver saw, and there was a 6-inch diameter puddle of oil on the floor upon startup.
Clues: Power appears OK, smoke emissions were greater than normal, but not severe, and cleared as the engine warmed. Fluid levels are OK and there are no fault codes in memory.

Vehicle: 2007 IH 4400 DT466
Key components: Hydraulic dump body, Allison automatic transmission
Scenario: This truck has a PTO-driven hydraulic pump with air-actuated controls for dump body operation. The dump body hydraulics consist of a “2 line” system where the pump oil supply is contained in the vented side of the hydraulic cylinder itself and there is no external reservoir or fluid return line. Since the vehicle was new, the pump has
suffered repeated premature leaks and failures.

Clues: The hydraulic oil was examined and found to be severely overheated but with no signs of abrasive wear. The PTO was tested and works correctly. The truck is programmed so that it cannot be driven while the PTO is engaged, and pump relief settings were verified correct. Pump RPM is programmed and confirmed correct. The hydraulic hoses are free of restriction and each new replacement pump corrected the condition for approximately one year.

Each month in Diagnose This! we present a real-life service scenario with clues as to what the ultimate diagnosis was. If you think you know the answer, be the first to e-mail Dsmith@rrpub.com with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.

Vehicle: 2007 IH 4400 DT466
Key components: Hydraulic dump body, Allison automatic transmission
Scenario: This truck has a PTO-driven hydraulic pump with air-actuated controls for dump body operation. The dump body hydraulics consist of a “2 line” system where the pump oil supply is contained in the vented side of the hydraulic cylinder itself and there is no external reservoir or fluid return line. Since the vehicle was new, the pump has
suffered repeated premature leaks and failures.

Clues: The hydraulic oil was examined and found to be severely overheated but with no signs of abrasive wear. The PTO was tested and works correctly. The truck is programmed so that it cannot be driven while the PTO is engaged, and pump relief settings were verified correct. Pump RPM is programmed and confirmed correct. The hydraulic hoses are free of restriction and each new replacement pump corrected the condition for approximately one year.

Vehicle: 2005 IH 4400
Key components: DT466 engine with exhaust gas recirculation (EGR), Allison transmission
Scenario: This truck fails to restart only when the engine is hot. When the engine is cold, it cranks excessively but eventually will start. Once warmed to operating temperature, if the engine is shut down, it cranks but fails to restart. The problem started as a hard, hot restart and gradually would no longer restart at all when hot.

Clues: Refer to the screenshot of scan data that was captured when the engine was hot and cranking, but not starting. It did not start during this attempt.

Each month in Diagnose This! we present a real-life service scenario with clues as to what the ultimate diagnosis was. If you think you know the answer, be the first to e-mail Dsmith@rrpub.com with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.

Vehicle: 2005 IH 4400
Key components: DT466 engine with exhaust gas recirculation (EGR), Allison transmission
Scenario: This truck fails to restart only when the engine is hot. When the engine is cold, it cranks excessively but eventually will start. Once warmed to operating temperature, if the engine is shut down, it cranks but fails to restart. The problem started as a hard, hot restart and gradually would no longer restart at all when hot.

Clues: Refer to the screenshot of scan data that was captured when the engine was hot and cranking, but not starting. It did not start during this attempt.

Each month in Diagnose This! we present a real-life service scenario with clues as to what the ultimate diagnosis was. If you think you know the answer, be the first to e-mail Dsmith@rrpub.com with the correct response for free Truck Parts & Service merchandise. The answer will be revealed in a future issue of the magazine.

Vehicle: 2005 IH 7400 flatbed with 95,000 miles

Key components: DT466 engine with exhaust gas recirculation (EGR), manual transmission

Scenario: Vehicle has very low power and barely reaches 40 miles per hour on level ground.
Clues: