| Table 1: | Resistance of AAT Sensor Unit |
Circuit Description
The ambient air temperature (AAT) sensor is located inside of the cab front panel.
The AAT sensor is a thermistor that changes a resistance signal to the engine control module (ECM) for optimization of fuel injection control.
DTC 0022 will set when the ECM detects an open circuit or sensor damage on the sensor signal circuit.
Conditions for Setting the DTC
The AAT sensor voltage exceeding 4.95 volts or lower than 0.1 volts for 1 second.
Action Taken When the DTC Sets
| • | Starting: Based on -20°C (-4°F) |
| • | Other: Based on 80°C (176°F) |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
DTC 0022 can be cleared by using the Clear Info on the scan tool or by using the Diag Clear Switch.
Diagnostic Aids
Inspect for the following conditions:
| • | Poor connection at the ECM |
| Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection. |
| • | Damaged harness |
| Inspect the wiring harness for damage, shorts to ground, shorts to battery, and open circuits. If the harness appears to be OK, observe the ambient air temperature display on the scan tool while moving connectors and wiring harnesses related to the AAT sensor. A change in the AAT scan tool display will indicate the location of the fault. |
| • | White smoke at engine start in cold districts |
Ambient Temperature | Resistance (kohms) |
|---|---|
20°C (68°F) | Near 3.8 (2.9 V) |
40°C (104°F) | 1.6 (1.9 V) |
60°C (140°F) | 0.8 (1.1 V) |
80°C (176°F) | 0.4 (0.7 V) |
Step | Action | Value | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||||||
1 |
Important: DTC 0022 may set at low atmospheric temperatures, less than -40°C (-40°F). Does DTC 0022 set while the ignition is ON or engine in operating? | -- | Go to Step 2 | Go to Diagnostic Aids | ||||
2 | Measure the voltage between pin number 53 and pin number 66 at the ECM harness connector C2 with the harness connected. Does the voltage measure the appropriate value within the specified range? | 0.1-4.8 V | Go to Step 4 | Go to Step 3 | ||||
3 | Inspect the connections at the AAT sensor harness. Is there a poor connection? | -- | Go to Step 9 | System OK | ||||
4 | Is there abnormally high or low ambient temperature? | -- | Go to Step 10 | Go to Step 5 | ||||
5 |
Does each resistance measure less than the specified value? | 2 ohms | Go to Step 6 | Go to Step 11 | ||||
6 | Measure resistance between pin number 53 at the ECM connector C2 and ground. Does the resistance measure more than the specified value? | 10 M ohms | Go to Step 7 | Go to Step 11 | ||||
7 |
Is the resistance within the value specified in the table? | -- | Go to Step 8 | Go to Step 12 | ||||
8 |
Does DTC 0022 reset? | -- | Go to Step 13 | System OK | ||||
9 | Repair AAT sensor wiring harness. Did you complete the repair? | -- | Go to Step 14 | -- | ||||
10 | Replace the ambient air temperature. Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
11 | Repair/replace the AAT sensor wiring harness. Did you complete the action? | -- | Go to Step 14 | -- | ||||
12 | Replace the AAT sensor assembly. Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
13 | Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data . Did you complete the replacement? | -- | Go to Step 14 | -- | ||||
14 |
Does DTC 0022 reset? | -- | Go to Step 2 | System OK | ||||
