DTC P2609 (Air Intake Heater) Troubleshooting

[Mr Coffee]

Hi,
Recently, my truck's (04 Ram 2500 w/ 5.9L) "check engine" light came on and the reader shows code P2609. I did a search and found the T/S instructions for code P2609, but couldn't find anything related to the symptoms I found... Everything checked out good, but when I measured the relay coil voltage (control signal from ECM) I only read +3.75 volts, referenced to ground, on both (relay #1 and #2) control lines. The T/S instructions have me jumper 12V to the coil to actuate the relays, so I assume that the ECM should supply 12V also? Does this mean I need to replace the ECM?

The truck seems to run ok and I haven't noticed any other problems or codes... Any suggestions?? I've heard that the air heater isn't all that important, since I live in the desert, but don't want to risk getting stranded if something else more important is also failed.

Thanks for any help!
Randy

 

[lpennock]

Check the voltage with the wire disconnected from the relays. If it is close to 12v then you need to check for a corroded connection.

 

[Mr Coffee]

Thanks for the response. That's how I measured the 3.75V. Now I'm wondering if the PCM needs the coils connected to have enough current to develop the full 12 volts?

The original issue that I thought caused the code was the terminal end at the battery(+), connecting the fusible links to the relays, was corroded and broke off disconnecting the voltage to the large terminal of the relays, but when I replaced it and reconnected it to the now clean battery, no luck... I wouldn't think that an open circuit would cause a voltage spike serious enough to take out the PCM. Is it possible?

 

[Bob4x4]

1.INTAKE AIR HEATER OPEN

1.	Measure the resistance between the intake air heater supply and ground terminal on each intake air heater.

Is the resistance less than 10 Ohms?

Yes
[h=4][/h]

1. Go To 2

No
[h=4][/h]

1. Replace the open Intake Air Heater.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

2.INTAKE AIR HEATER GROUND OPEN

1.	Measure the resistance of the intake air heater ground circuit between the intake air heater terminal and the intake manifold cover ground connection.

NOTE:

The intake air heater circuit is grounded through a conductive gasket on the top and bottom of the air heater (grey colored gaskets).

Is the resistance less than 10 Ohms?

Yes
[h=4][/h]

1. Go To 3

No
[h=4][/h]

1. Repair the open Intake Air heater ground or replace both heater gaskets with the proper conductive gaskets.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

3.OPEN BATTERY CABLE FROM INTAKE AIR HEATER RELAY

1.	Measure the resistance of the battery cable between the intake air heater and the intake air heater relay for both intake air heaters.

Is the resistance less than 10 Ohms?

Yes
[h=4][/h]

1. Go To 4

No
[h=4][/h]

1. Repair The open or high resistance battery cable from the intake heater relay to heater.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

4.BATTERY CABLE OPEN

1.	Measure the resistance of the battery cable between the battery and the intake air heater relay for both relays.

Is the resistance less than 10 Ohms?

Yes
[h=4][/h]

1. Go To 5

No
[h=4][/h]

1. Replace the battery cable from the battery to the Intake Air Heater Relay.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

5.#1 INTAKE AIR HEATER RELAY

1.	Disconnect the #1 intake air heater relay signal wire.

2.	Connect a jumper wire from the signal terminal of the #1 intake air heater relay to battery positive.

Did the relay click when 12 volts was applied?

Yes
[h=4][/h]

1. Go To 6

No
[h=4][/h]

1. Replace #1 Intake Air Heater Relay.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

6.#2 INTAKE AIR HEATER RELAY

1.	Disconnect the #2 intake air heater relay signal wire.

2.	Connect a jumper wire from the signal terminal of the #2 intake air heater relay to battery positive.

Did the relay click when 12 volts was applied?

Yes
[h=4][/h]

1. Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

No
[h=4][/h]

1. Replace #2 Intake Air Heater Relay.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedur

1.INTAKE AIR HEATER OPEN

1.	Measure the resistance between the intake air heater supply and ground terminal on each intake air heater.

Is the resistance less than 10 Ohms?

Yes
[h=4][/h]

1. Go To 2

No
[h=4][/h]

1. Replace the open Intake Air Heater.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

2.INTAKE AIR HEATER GROUND OPEN

1.	Measure the resistance of the intake air heater ground circuit between the intake air heater terminal and the intake manifold cover ground connection.

NOTE:

The intake air heater circuit is grounded through a conductive gasket on the top and bottom of the air heater (grey colored gaskets).

Is the resistance less than 10 Ohms?

Yes
[h=4][/h]

1. Go To 3

No
[h=4][/h]

1. Repair the open Intake Air heater ground or replace both heater gaskets with the proper conductive gaskets.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

3.OPEN BATTERY CABLE FROM INTAKE AIR HEATER RELAY

1.	Measure the resistance of the battery cable between the intake air heater and the intake air heater relay for both intake air heaters.

Is the resistance less than 10 Ohms?

Yes
[h=4][/h]

1. Go To 4

No
[h=4][/h]

1. Repair The open or high resistance battery cable from the intake heater relay to heater.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

4.BATTERY CABLE OPEN

1.	Measure the resistance of the battery cable between the battery and the intake air heater relay for both relays.

Is the resistance less than 10 Ohms?

Yes
[h=4][/h]

1. Go To 5

No
[h=4][/h]

1. Replace the battery cable from the battery to the Intake Air Heater Relay.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

5.#1 INTAKE AIR HEATER RELAY

1.	Disconnect the #1 intake air heater relay signal wire.

2.	Connect a jumper wire from the signal terminal of the #1 intake air heater relay to battery positive.

Did the relay click when 12 volts was applied?

Yes
[h=4][/h]

1. Go To 6

No
[h=4][/h]

1. Replace #1 Intake Air Heater Relay.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

6.#2 INTAKE AIR HEATER RELAY

1.	Disconnect the #2 intake air heater relay signal wire.

2.	Connect a jumper wire from the signal terminal of the #2 intake air heater relay to battery positive.

Did the relay click when 12 volts was applied?

Yes
[h=4][/h]

1. Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedure)

No
[h=4][/h]

1. Replace #2 Intake Air Heater Relay.
2. Perform POWERTRAIN VERIFICATION TEST - DIESEL. (Refer to 28 - DTC-Based Diagnostics/MODULE, Engine Control (ECM) - Standard Procedur

 

[lpennock]

Thanks for the response. That's how I measured the 3.75V. Now I'm wondering if the PCM needs the coils connected to have enough current to develop the full 12 volts?

The original issue that I thought caused the code was the terminal end at the battery(+), connecting the fusible links to the relays, was corroded and broke off disconnecting the voltage to the large terminal of the relays, but when I replaced it and reconnected it to the now clean battery, no luck... I wouldn't think that an open circuit would cause a voltage spike serious enough to take out the PCM. Is it possible?

I would think you should have 12V open circuit when the conditions are correct to turn on the grid heater. You could try disconnecting the batteries for about 10min to reset the computer.

 

[PWong]

Thanks for the response. That's how I measured the 3.75V. Now I'm wondering if the PCM needs the coils connected to have enough current to develop the full 12 volts?

The original issue that I thought caused the code was the terminal end at the battery(+), connecting the fusible links to the relays, was corroded and broke off disconnecting the voltage to the large terminal of the relays, but when I replaced it and reconnected it to the now clean battery, no luck... I wouldn't think that an open circuit would cause a voltage spike serious enough to take out the PCM. Is it possible?

ECM sends 12V to heater relay only when IAT inlet air temp reads below 66F.
You can put the IAT (the one before the turbo) in a cup of ice cube/water to start the test.

When ECM sends 12V to the relay, 12V should be there ALL the time with relay connected and energized.
Otherwise ECM is defective in the relay operation.

 

[vlotta]

When conditions aren't meet to require the grid heaters what should be the voltage at the relay. My ECM is also sending low voltage 3.6 volts. I tried putting IAT into Ice water and nothing changed.

 

[Prairie Dog]

I think the 3V is there so the ECM can check for a bad coil.