Battery Power or Ground to the ECM

TM 9-2320-312-24-2

Troubleshooting Section

Battery Power or Ground to the

If the engine can not reach the programmed Top

Engine Limit, check the duty cycle of the accelerator

ECM

pedal position sensor in order to ensure that the

duty cycle is within calibration (75 to 90 Percent

1. Ensure that the following connectors have been

at high idle).

installed correctly:

If the accelerator pedal position is unstable,

ECM connectors (J1/P1 and J2/P2)

check the duty cycle of the accelerator pedal

position sensor. Check the duty cycle of the

Injector connector (J300/P300)

accelerator pedal position sensor by slowly

operating the accelerator pedal in order to verify

Camshaft position sensor connector

that the accelerator pedal position sensor is within

(J401/P401 and J402/P402)

calibration. The accelerator pedal position sensor

is within calibration when both of the following

2. Use the electronic service tool to check for a

conditions are met:

diagnostic code 168-02 (Intermittent Battery

Power to the ECM). Check the power connections

10 to 22 percent at low idle

for the ECM and the ground connections for the

ECM. If a problem is suspected, wire a bypass.

75 to 90 percent at high idle

Refer to Troubleshooting, "Ignition Key Switch

Circuit and Battery Supply Circuit - Test"(51).

Also, ensure that the duty cycle changes as the

pedal position changes.

Electronic System

If a problem with the accelerator pedal position

1. Connect the electronic service tool to the cab

sensor is suspected, refer to Troubleshooting,

data link connector.

"Accelerator Pedal (Throttle) Position Sensor Circuit

- Test".

2. Monitor the fuel position, the rated fuel limit and

the FRC fuel limit.

Vehicle Speed Signal

While the vehicle is operating under full load, the

Monitor the vehicle speed signal. Ensure the

parameters should meet the following conditions:

accuracy of the vehicle speed signal by comparing

the vehicle speed signal to the actual vehicle speed.

The fuel position is equal to the rated fuel limit.

If the vehicle speed is greater than the "VSL", the

The fuel position is less than the FRC fuel limit.

Power is limited. If a problem is discovered, refer to

Troubleshooting, "Vehicle Speed and Speedometer

If the fuel position is equal to the rated fuel limit

Circuit - Test".

and the fuel position is less than the FRC fuel

limit, the electronics are operating correctly.

Power Train Data Link

Proceed to "Vehicle Speed Signal".

1. Check the "Powertrain Data Link". Ensure that

3. If the fuel position is not equal to the rated fuel

the SAE J1939 data link is not limiting the power.

limit and/or the fuel position is not less than the

FRC fuel limit, perform the following tests in

2. Connect the electronic service tool to the cab

order:

data link connector.

4. When the engine is off, turn the ignition key

3. Monitor the "Powertrain Data Link" status screen

switch to the ON position. Check the boost

while the vehicle is experiencing problems.

pressure on the electronic service tool status

screen.

If the "Powertrain Data Link" status screen

indicates that the data link is limiting the power or

When the engine is off, the boost pressure

the rpm, verify that this is not normal operation. If

should be 0 kPa (0 psi).

this is not normal operation, refer to the vehicle

OEM for repairs.

Accelerator Pedal Position Sensor

Fuel Supply

Monitor the status of the accelerator pedal position

sensor. Operate the engine at high idle with the

1. Monitor the exhaust for smoke while the engine

vehicle in neutral.

is being cranked.