28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM), 6.7L/Diagnosis and Testing

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 post heat 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) monitors the battery system voltage and looks for a calibrated drop when the Intake Air Heater is commanded on. The fault is set if the ECM detects a voltage difference below the calibrated value when the Intake Air Heater circuit is commanded on and off during the preheat cycle at key on.

Possible Causes

(A19) AUXILIARY BATTERY CIRCUIT OPEN/HIGH RESISTANCE
(A58) INTAKE AIR HEATER CIRCUIT OPEN/HIGH RESISTANCE
INTAKE AIR HEATER RELAY
INTAKE AIR HEATER

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.(Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

1.ACTIVE DTC

NOTE: / A loose or poor connection at the Battery Ground Cable or at the terminals on the Intake Air Heater Relay terminals may cause this code to set.
1. / Ignition on, engine not running.
2. / With the scan tool check for active DTCs.

Is the DTC active?
Yes

  • Go To2

No

  • Perform the INTERMITTENT CONDITION diagnostic procedure.

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 on.
2. / Using a voltmeter, probe the (A19) Auxiliary Battery circuit at the Intake Air Heater Relay terminal.
NOTE: / It is important for the circuit to be connected and carrying a load during testing. For best results, do not disconnect the circuit at any time during this test procedure.
3. / Using a scan tool, actuate the Cold Start Aid Driver 1 Output circuit.NOTE:Set the actuation to toggle.
4. / Monitor the reading on the voltmeter while the Intake Air Heater circuit is toggling on and off.Monitor the circuit and let the actuation run until it times out.
NOTE: / The meter should read equivalent to battery voltage during the entire actuation.

Does the voltmeter read as described in the note above?
Yes

  • Go To3

No

  • Repair the (A19) Auxiliary Battery circuit for an open or high resistance. If the Fusible Link is found to be blown, check for a short to ground on the entire (A19) Auxiliary Battery circuit and (A58) Intake Air Heater circuit.
  • Perform the POWERTRAIN VERIFICATION TEST - 6.7L.

3.CHECK THE INTAKE AIR HEATER RELAY

CAUTION: / Excessive actuation to the Intake Air Heater may overheat and damage the heater assembly. Allow the Intake Air heater to cool for five minutes between each actuation procedure to prevent any possible damage from overheating to occur to the Intake Air Heater.
1. / Move the voltmeter to the (A58) Intake Air Heater circuit terminal on the Intake Air Heater.
2. / Using a scan tool, actuate the Cold Start Aid Driver 1 Output circuit.
NOTE: / Set the actuation to toggle.
3. / Monitor the reading on the voltmeter while the Intake Air Heater circuit is toggling on and off.Monitor the circuit and let the actuation run until it times out.
NOTE: / The meter should read equivalent to battery voltage when the circuit is toggled on, and near zero volts when the circuit is toggled off.

Does the voltmeter read as described in the note above?
Yes

  • Go To4

No

  • Replace the Intake Air Heater Relay in accordance with the service information.
  • Perform the POWERTRAIN VERIFICATION TEST - 6.7L.(Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure).

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

CAUTION: / Excessive actuation to the Intake Air Heater may overheat and damage the heater assembly. Allow the Intake Air heater to cool for five minutes between each actuation procedure to prevent any possible damage from overheating to occur to the Intake Air Heater.
1. / Move the voltmeter to the (A58) Intake Air Heater circuit connection at the Intake Air Heater.
2. / Using a scan tool, actuate the Cold Start Aid Driver 1 Output circuit.NOTE:Set the actuation to toggle.
3. / Monitor the reading on the voltmeter while the Intake Air Heater circuit is toggling on and off.Monitor the circuit and let the actuation run until it times out.
NOTE: / The meter should read equivalent to battery voltage when the circuit is toggled on, and near zero volts when the circuit is toggled off.

Does the voltmeter read as described in the note above?
Yes

  • Replace the Intake Air Heater in accordance with the service information

No

  • Repair the (A58) Intake Air Heater circuit for an open or high resistance.