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P2609






P2609-INTAKE AIR HEATER SYSTEM PERFORMANCE





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

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 the battery to heat the grid heater elements causing the battery voltage to drop. The intake air heater diagnostic 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 Powertrain Control Module (PCM) will light the MIL lamp when the diagnostic runs and fails. The PCM will turn off the MIL lamp when the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
While the wait to start lamp is illuminated.

- Set Condition:
Powertrain Control Module (PCM) does not detect a voltage drop in battery system voltage when Intake Air Heater circuit is commanded on during the preheat cycle.





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. CHECK THE (A19) AUXILIARY BATTERY CIRCUIT FOR AN OPEN/HIGH RESISTANCE





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

3. CHECK THE (A58) INTAKE AIR HEATER CIRCUIT FOR AN OPEN/HIGH RESISTANCE




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 (A58) Intake Air Heater circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

4. CHECK THE (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. CHECK THE (K174) INTAKE AIR HEATER RELAY CONTROL CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn ignition off.
2. Disconnect the PCM 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 PCM C2 harness connector.

Is the resistance less than 5.0 Ohms?

Yes

- Go To 6

No

- Repair the (K174) Intake Air Heater Relay Control circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. CHECK THE (K174) INTAKE AIR HEATER RELAY CONTROL CIRCUIT FOR A SHORT TO GROUND




1. 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 (K174) Intake Air Heater Relay Control circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

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

7. CHECK THE (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. CHECK THE (K974) INTAKE AIR HEATER RELAY CONTROL RETURN CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Turn ignition off.
2. Disconnect the PCM 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 PCM C2 harness connector.

Is the resistance less than 5.0 Ohms?

Yes

- Go To 9

No

- Repair the (K974) Intake Air Heater Relay Control circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

9. CHECK THE (K974) INTAKE AIR HEATER RELAY CONTROL RETURN CIRCUIT FOR A SHORT TO GROUND




1. 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 (K974) Intake Air Heater Relay Control circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

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

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