Air Inlet Heater Circuit

151

TM 9-2320-312-24-2

Troubleshooting Section

The air inlet heater

B. Remove the signal wire for the accelerator pedal

position sensor from the ECM Connector P1:66.

The air inlet heater relay

C. Remove terminal "C" (Accelerator Pedal Position)

The lamp for the air inlet heater

from the accelerator pedal position sensor

connector.

The following background information is related

D. Route new wiring from the ECM to the accelerator

to the following procedure:

pedal position sensor.

The use of the air inlet heater improves the engines'

E. Turn the ignition key switch to the ON position.

ability to start when the engine is cold. A reduction

of white smoke is also a benefit of the air inlet heater.

F. Check the duty cycle of the accelerator pedal

position sensor on ET while the accelerator pedal

The ECM controls the operation of the air inlet heater

assembly is being moved over the full range.

and the ECM controls the operation of the lamp for

the air inlet heater through the air inlet heater relay.

Expected Result:

The operation of the air inlet heater is determined

The duty cycle is between 10 and 22 percent with

by three different cycle times:

the accelerator pedal assembly in the Low Idle

ECM Powerup and Preheat Cycle

position, and the duty cycle is between 75 and 90

percent with the accelerator pedal assembly in the

Cranking

High Idle position.

Engine Started

Results:

The cycle time is determined by the following

parameters:

Repair: Perform the following repair:

Engine parameters

The wiring from the ECM to the accelerator pedal

Vehicle speed

position sensor appears faulty. Permanently install

new wiring.

Service brake

Verify that the repair eliminates the problem.

Effects of Vehicle Speed on the Operation of the

STOP.

Air Inlet Heater and on the Operation of the Brake

Pedal Position.

Not OK Double check the wiring, the ECM

The air inlet heater is turned off when the brake

vehicle harness connector J1/P1 and the sensor

pedal is depressed and the vehicle speed is equal

connector. If a problem still exists, restart the test

to 8 km/h (5 mph) or greater than 8 km/h (5 mph).

procedure. STOP.

If a diagnostic code for the vehicle speed sensor is

i01857574

active, the ECM will assume that the vehicle speed

Air Inlet Heater Circuit - Test

is above 8 km/h (5 mph). If an active diagnostic

code is triggered for the vehicle speed sensor, the

ECM will disable the heater when the brakes are

SMCS Code: 1090-081

applied.

System Operation Description:

The ECM Powerup and Preheat Cycle.

Use this procedure under the following situation:

The lamp for the air inlet heater should turn on for

a minimum of 2 seconds when the ECM is first

Use the following information in order to troubleshoot

powered up. The lamp should turn on regardless of

the air inlet heater circuit when there is an active

the coolant temperature. The ECM will signal the air

code:

inlet heater to stay on for 30 seconds if the sum of

the coolant temperature and the inlet manifold air

70-05 Inlet Air Heater Open Circuit (49)

temperature is less than 25 degrees Celsius or 109

degrees Fahrenheit.

70-06 Inlet Air Heater Short Circuit (49)

This procedure can also be used to troubleshoot

the following components: