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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. An Intake Air Heater is used for this purpose. The Intake Air Heater works in two phases, preheat phase (before engine starts) and postheat phase (after engine starts). Preheat phase typically heats the Intake Air Heater coil during the key-on for about 10 seconds to 30 seconds depending on inlet air temperature. The PCM controls Intake Air Heater operation with the Intake Air Heater Relay, which is located directly behind the air filter box under the fresh air hose. The Intake Air Heater Relay is not a typical type of relay due to the amount of current passing through it. The Intake Air Heater Relay visually resembles a solenoid in appearance. The Intake Air Heater monitor looks for a change in battery voltage as the heater is turned on and off during preheat, to indicate proper operation. The Powertrain Control Module (PCM) will light the MIL lamp when the monitor runs and fails. The PCM will turn off the MIL lamp when the monitor 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 - 6.7L 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. 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 (K174) INTAKE AIR HEATER RELAY CONTROL CIRCUIT
1. Turn ignition on, engine not running.
2. Disconnect the (K174) Intake Air Heater Relay Control circuit connector at the Intake Air Heater Relay.
3. Using a scan tool, actuate the Cold Start Aid Driver 1 Output circuit.
4. With a 12-Volt test light connected to ground, probe the (K174) Intake Air Heater Relay Control circuit at the connector.

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

Does the test light illuminate brightly?

Yes

- Go To 6

No

- Go To 4

4. 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 and the PCM C2 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 5

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.

5. 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 Control circuit connector at the Intake Air Heater Relay.

Is the resistance below 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 Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

6. CHECK THE (K974) INTAKE AIR HEATER RELAY CONTROL RETURN CIRCUIT
1. Turn ignition off.
2. Disconnect the (K974) Intake Air Heater Relay Control Return circuit connector at the Intake Air Heater Relay.
3. With a 12-Volt test light connected to battery positive, probe the (K974) Intake Air Heater Relay Control Return circuit at the connector.

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

Does the test light illuminate brightly?

Yes

- Go To 8

No

- Go To 7

7. 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 (K974) Intake Air Heater Relay Control Return circuit connector and the PCM C2 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- 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.

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.

8. CHECK THE INTAKE AIR HEATER RELAY




1. Reconnect the (K974) Intake Air Heater Relay Control Return circuit connector and the (K174) Intake Air Heater Relay Control circuit connector at the Intake Air Heater Relay.
2. Turn ignition on, engine not running.
3. Using a scan tool, actuate the Cold Start Aid Driver 1 Output circuit.
4. Disconnect the Intake Air Heater harness connector.
5. With a 12-Volt test light connected to ground, probe the (A58) Intake Air Heater 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

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

9. CHECK THE (A58) INTAKE AIR HEATER CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Disconnect the Intake Air Heater connector.
2. Using a scan tool, actuate the Cold Start Aid Driver 1 Output circuit.
3. With a 12-Volt test light connected to ground, probe the (A58) Intake Air Heater circuit at the Intake Air Heater connector.

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.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

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

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