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P2609






P2609-INTAKE AIR HEATER SYSTEM PERFORMANCE





For a complete wiring diagram, refer to the Wiring Information Electrical Diagrams.

Theory of Operation

Heating the inlet air during cold temperatures will increase the fuel efficiency and improves system performance. Grid heaters are used for this purpose. The grid heater works in two phases, preheat phase (before engine starts) and postheat phase (after engine starts). Preheat phase typically heats the grid heater coil during the key-on for about 10 seconds to 30 seconds depending on inlet air temperature. During grid heater operation, the intake air heater system draws current from battery to heat the grid heater elements forcing the battery voltage to drop. The intake air heater monitor looks at the change in battery voltage as the grids are turned on and off during preheat, to indicate proper functioning of the grids. The Engine Control Module (ECM) will light the MIL lamp when the diagnostic runs and fails in two consecutive drive cycles. The ECM will turn off the MIL lamp when the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
First 30 seconds of engine operation.

- Set Condition:
Engine Control Module (ECM) does not detect a voltage drop in battery system voltage when Intake Air Heater circuit is commanded on.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure

Diagnostic Test

1. ACTIVE DTC
1. Ignition on, engine not running.
2. With the scan tool check for active DTCs.

Is the DTC active?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. (A19) AUXILIARY BATTERY CIRCUIT OPEN





NOTE: A loose or poor Battery Ground Cable connection may cause this code to set.

1. Turn ignition off.
2. Remove Intake Air Heater relay.
3. With a 12-volt test light connected to ground, probe the (A19) auxiliary battery circuit at the Intake Air Heater relay.

NOTE: Compare the test light brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?

Yes

- Go To 3

No

- Repair the open or high resistance in the (A19) Auxiliary Battery circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

3. (A58) INTAKE AIR HEATER CIRCUIT OPEN




1. Intake Air Heater relay still removed.
2. Turn ignition on, engine not running.
3. Connect a jumper across terminals 85 and 86 at the Intake Air Heater relay connector.
4. With a 12-volt test light connected to ground, probe the (A58) Intake Air Heater circuit at the Intake Air Heater.

NOTE: Compare the test light brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?

Yes

- Go To 4

No

- Repair the open in the (A58) Intake Air Heater circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. (K174) INTAKE AIR HEATER RELAY CONTROL CIRCUIT




1. Intake Air Heater relay still removed.
2. Turn ignition on, engine not running.
3. Using a scan tool, actuate the Intake Air Heater relay.
4. With a 12-volt test light connected to ground, probe the (K174) Intake Air Heater relay control circuit.

NOTE: Compare the test light brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?

Yes

- Go To 7

No

- Go To 5

5. (K174) INTAKE AIR HEATER RELAY CONTROL CIRCUIT OPEN




1. Turn ignition off.
2. Disconnect the ECM C2 harness connector.
3. Measure the resistance of the (K174) Intake Air Heater relay Control circuit between the Intake Air Heater relay connector and the ECM C2 harness connector.

Is the resistance less than 10.0 Ohms?

Yes

- Go To 6

No

- Repair the open in the (K174) Intake Air Heater relay control circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. (K174) INTAKE AIR HEATER RELAY CONTROL CIRCUIT SHORTED TO GROUND




1. Ignition off.
2. Measure resistance between ground and the (K174) Intake Air Heater relay control circuit at the Intake Air Heater relay connector.

Is the resistance less than 10k Ohms?

Yes

- Repair the short to ground in the (K174) Intake Air Heater relay control circuit.
- Perform POWERTRAIN VERIFICATION TEST (DIESEL). Powertrain Verification Test.

No

- Inspect ECM C2 connector for spread or pushed out terminals before replacing ECM. If connector and terminals look ok, replace the ECM.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

7. (K974) INTAKE AIR HEATER RELAY CONTROL RETURN CIRCUIT




1. Intake Air Heater relay still removed.
2. Turn ignition on.
3. Using a scan tool, actuate the Intake Air Heater relay.
4. With a 12-volt test light connected to battery positive, probe the (K974) Intake Air Heater relay control circuit.

NOTE: Compare the test light brightness to that of a direct connection to the battery.

Does the test light illuminate brightly?

Yes

- Replace the Intake Air Heater relay.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 8

8. (K974) INTAKE AIR HEATER RELAY CONTROL RETURN CIRCUIT OPEN




1. Turn ignition off.
2. Disconnect the ECM C2 harness connector.
3. Measure the resistance of the (K974) Intake Air Heater relay control return circuit between the Intake Air Heater relay connector and the ECM C2 harness connector.

Is the resistance less than 10.0 Ohms?

Yes

- Go To 9

No

- Repair the open in the (K974) Intake Air Heater relay control return circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

9. (K974) INTAKE AIR HEATER RELAY CONTROL RETURN CIRCUIT SHORTED TO GROUND




1. Ignition off.
2. ECM C2 harness connector disconnected.
3. Measure resistance between ground and the (K974) Intake Air Heater relay control circuit at the Intake Air Heater relay connector.

Is the resistance less than 10k Ohms?

Yes

- Repair the short to ground in the (K974) Intake Air Heater relay control circuit.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Inspect ECM C2 connector for spread or pushed out terminals before replacing ECM. If connector and terminals look ok, replace the ECM.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

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