C9 Marine Auxiliary and Marine Generator Set Engines Caterpillar

Use this procedure to troubleshoot any suspect problems with the air inlet heater circuit.

This procedure covers the following diagnostic codes:

• 617-05 Air Inlet Heater Relay open/current below normal

• 617-06 Air Inlet Heater Relay grounded/current above norm

The air inlet heater improves the engine's ability to start when the engine is cold. A reduction of white smoke is also a benefit of the air inlet heater. The air inlet heater is disabled when ether is used to start the engine.

The Electronic Control Module (ECM) activates the air inlet heater via the air inlet heater relay. The air inlet heater is activated according to the following cycles:

• Power up cycle

• Preheat cycle

• Crank cycle

• Running cycle

• Postheat cycle

Power Up Cycle - The ECM activates the air inlet heater for two seconds after the ECM is first powered up regardless of temperature or engine speed.

Preheat Cycle - If the coolant temperature is less than 49 °C (120 °F), the ECM activates the air inlet heater for 30 seconds. If the operator attempts to start the engine before the end of the preheat cycle, the ECM will begin using the strategy for the crank cycle.

Crank Cycle - When the engine is cranking and the coolant temperature is less than 49 °C (120 °F), the air inlet heater will remain on while the engine is cranking. If the engine fails to start, the ECM will revert to the preheat cycle.

Running Cycle - The air inlet heater will remain on after the engine has started. If the coolant temperature does not reach 49 °C (120 °F) within five minutes, the ECM will use the postheat cycle.

Postheat Cycle - The air inlet heater will cycle on and off if the coolant temperature is still less than 49 °C (120 °F). The heater will turn on for 30 seconds. Then, the heater will turn off for 10 seconds. This cycle continues for 15 minutes. The cycle ends if the coolant temperature exceeds 49 °C (120 °F).

Illustration 1	g00956306
Typical component locations

Illustration 2	g01043564
Typical schematic for the air inlet heater

Illustration 3	g01172773
P2 ECM connector

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Turn the keyswitch to the OFF position.

2. Thoroughly inspect the J501/P501 air inlet heater relay connectors and connector (4). Inspect the connections on air inlet heater relay (2) and air inlet heater (1). Refer to Troubleshooting, "Electrical Connectors - Inspect".

3. Perform a 45 N (10 lb) pull test on each of the wires in the connectors that are associated with the circuit.

4. Check the torque of the allen head screws for the ECM connectors. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

5. Check the harness and wiring for abrasion and for pinch points from the air inlet heater back to the ECM and from the air inlet heater back to the battery.

Expected Result:

All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The harness and the connectors appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem with the connectors and/or the wiring.

  Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled. Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".

2. Turn the keyswitch to the ON position.

3. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 15 seconds so that any codes may become active. Look for these codes:
   • 617-05

   • 617-06

Expected Result:

One of the above codes is active.

Results:

• Active 617-05 code - A 617-05 diagnostic code is active. Proceed to Test Step 3.

• Active 617-06 code - A 617-06 diagnostic code is active. Proceed to Test Step 5.

• No active codes - None of the above codes are active. There may be a problem with the high power circuit. Proceed to Test Step 6.

Test Step 3. Check for an Open Circuit to the Relay

Show/hide table



Illustration 4	g01118589
Small terminals for the typical air inlet heater relay

1. Disconnect the wires from the small terminals of the air inlet heater relay.

2. Install a test lamp across the wires.

3. Start the "Air Inlet Heater Override" on Cat ET and observe the test lamp.

   Note: Do not leave the "Air Inlet Heater Override" ON. This prevents unnecessary cycling of the air inlet heater and the battery from discharging. The "Air Inlet Heater Override" has a one minute timer that disables the test when the time expires.

4. Stop the "Air Inlet Heater Override" and turn the keyswitch to the OFF position.

Expected Result:

The test lamp turned on while the override was active.

Results:

• OK - The test lamp turned on while the override was active. The open circuit is in the relay.

  Repair: Replace the air inlet heater relay. Clear any diagnostic codes. Verify that the problem is resolved.

  STOP

• Not OK - The test lamp did not turn on while the override was active. Proceed to Test Step 4.

Test Step 4. Check the Wiring To the Relay

1. Disconnect the J2/P2 connectors.

Note: Be sure to wiggle the harness during the following measurements in order to reveal an intermittent condition.

2. Measure the resistance between the +Battery terminal and P501-1.

3. Measure the resistance between terminals P2-8 and P501-2.

Expected Result:

Both of the resistance measurements are less than ten Ohms.

Results:

• OK - Both of the resistance measurements are less than ten Ohms.There may be a problem with the ECM

  Repair: Replace the ECM.

  STOP

• Not OK - At least one of the resistance measurements is more than ten Ohms. There is a problem with the wiring to the air inlet heater relay. There may be a problem with a connector.

  Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 5. Check for a Short Circuit in the Wiring to the Relay

Show/hide table



Illustration 5	g01118589
Small terminals for the typical air inlet heater relay

1. Disconnect the wires from the small terminals for the air inlet heater relay.

2. Turn the keyswitch to the ON position.

3. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 15 seconds so that any codes may become active.

4. Turn the keyswitch to the OFF position.

Expected Result:

The short circuit diagnostic code (617-06) changed to an open circuit diagnostic code (617-05) when the wires to the relay were disconnected.

Results:

• OK - The short circuit diagnostic code (617-06) changed to an open circuit diagnostic code (617-05) when the wires to the relay were disconnected. The short circuit is in the relay.

  Repair: Replace the relay. Clear the diagnostic codes.Verify that the problem is resolved.

  STOP

• Not OK - The short circuit diagnostic code (617-06) remained when the wires to the relay were disconnected. There is a problem in the wiring between the ECM and the relay. There may be a problem with a connector.

  Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 6. Check for Battery Voltage at the Relay

1. Connect a test lamp between the +Battery side of the air inlet heater relay and the engine ground.

Expected Result:

The test lamp turns ON.

Results:

• OK - The test lamp turns ON. Battery voltage is reaching the relay. Proceed to Test Step 6.

• Not OK - The test lamp does not turn ON. Battery voltage is not reaching the relay.

  Repair: There is an open circuit in the wiring between the battery and the relay. There may be a problem with a connection.Repair the wire and/or the connection, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 7. Check for Voltage Output at the Relay

1. Connect a test lamp between the output terminal of the air inlet heater relay and the engine ground.

   Note: Observe the test lamp. The test lamp should be off, since the relay is not energized. If the test lamp is on, ensure that the test lamp is connected to the output side of the relay.

2. Turn the keyswitch to the ON position.

3. Run the "Air Inlet Heater Override" on Cat ET and observe the test lamp.

   Note: Do not leave the "Air Inlet Heater Override" ON. This prevents unnecessary cycling of the air inlet heater and the battery from discharging. The "Air Inlet Heater Override" has a one minute timer that disables the test when the time expires.

4. Stop the "Air Inlet Heater Override" and turn the keyswitch to the OFF position.

Expected Result:

The test lamp turned on when the "Air Inlet Heater Override" was enabled.

Results:

• OK - The test lamp turned on when the "Air Inlet Heater Override" was enabled. The air inlet heater relay and the +Battery connection to the air inlet heater relay are operating correctly. Proceed to Test Step 8.

• Not OK - The test lamp did not turn on when the "Air Inlet Heater Override" was enabled.

  Repair: Replace the relay.Verify that the problem is resolved.

  STOP

Test Step 8. Check the Wiring Between the Relay and the Heater and Between the Heater and the Engine Block

Show/hide table



Illustration 6	g01143674
Typical left side view (1) Wire (2) Terminal

1. Measure the resistance of wire (1) that connects the relay to the air inlet heater.

2. Measure the resistance of the ground strap that is connected between terminal (2) and the engine block.

Expected Result:

Both of the resistance measurements are less than ten Ohms.

Results:

• OK - Both of the resistance measurements are less than ten Ohms. Proceed to Test Step 9.

• Not OK - At least one of the resistance measurements is more than ten Ohms. There is an open circuit in the wiring. There may be a problem with a connector.

  Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

  STOP

Test Step 9. Measure the Current through the Heater

Show/hide table



Illustration 7	g01118617
Typical left side view (1) Wire (2) Terminal (3) Terminal

1. Connect a 155-5176 AC/DC Current Probe or an equivalent inductive pickup clamp around wire (1) between the relay and the air inlet heater.

2. Connect the current probe to a multimeter.

3. Turn the keyswitch to the ON position.

4. Run the "Air Inlet Heater Override" on Cat ET and observe the current reading on the multimeter.

   Note: Do not leave the "Air Inlet Heater Override" On. Avoid unnecessary cycling of the air inlet heater in order to prevent the battery from discharging. The "Air Inlet Heater Override" has a one minute timer in order to disable the test when the time expires.

5. While the override is active, measure the voltage between terminals (2) and (3) .

6. Stop the "Air Inlet Heater Override" and turn the keyswitch to the OFF position.

Expected Result:

The current reading is between 84 and 104 Amperes. The voltage reading is approximately 22 VDC.

Note: If the voltage reading does not match the specified value, you will need to adjust the current value accordingly. For slightly lower voltages, the current value will be slightly lower. For slightly higher voltages, the current value will be slightly higher.

Results:

• OK - The readings are within the specified ranges.

  Repair: The readings are within the specified ranges. The air inlet heater circuit appears to be operating correctly at this time. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage reading and/or the current reading is not within the specified ranges.

  Repair: Replace the air inlet heater.Verify that the problem is resolved.

  STOP