P2609- No power from ECM to heater relay

[ajpulley]

The other morning, it was real cold, maybe 13F, and I started the truck after waiting a few seconds. Ever since, the MIL has been on. After troubleshooting the diagnostic code, P2609, that was associated with the MIL, I found no voltage from the ECM to one of the intake heater relays at the relay itself. I tested the battery-to-relay cables/fuse links, relay-to-heater cables, grid heaters, and grounds. Finally found no voltage on the load of one of the relays, then no voltage from ECM to turn the relay on. I have not been able to check the C130 or C2 connectors yet.

Anyone who's a technician/mechanic have any experience with this, or suggestions? I'd hate to have to replace the Cummins computer.

 

[Bob4x4]

Rethink your trouble shooting. The gridheater only gets powered up when cold at start up. You probably have weak or bad Batt(s). Get the batteries tested first.

 

[Prairie Dog]

Welcome to the forum, it sounds like you've done some good trouble shooting. So I take it the other heater relay works? If so then you may want to try disconnecting the offending relay and doing a resistance measurement across its coil. If it's open the ECM may see this as a fault and stop supplying power to it.
This would be a good subject for Sag2 to chime in on ~ Sag are you out there?

 

[ajpulley]

Yes, I did extensively troubleshoot, with the help of the Mopar service manual. According to the wiring diagram, the ECM supplies a separate wire to each relay coil. The other side of the relay coil is grounded. When turning the key to the on position, the ECM is sending +/-12VDC to the one relay that works when the wait-to-start light illuminates. The other relay is not receiving its 12VDC. Again, I still have to find some time to make sure there isn't a break in the wire between the relay coil and the C130 connector, and between the C130 connector and the C2 connector of the ECM. Though I don't see a reason for those two harnesses to have an open wire, it still is a possibility until I rule it out.

Moreover, maybe what I should be asking is how frequent do Cummins' ECMs fail, for any reason and not specifically this reason? Of the forums I've read since I bought the truck new, I very rarely read about a failed ECM, or a function of the ECM failing though it may still run the truck in general.

 

[ajpulley]

Bob4x4, I'm an experienced commercial/industrial electrician. I've read through Mopar's service manual and schematic. While the heaters are supplied by the batteries directly, the relay coils are controlled by the ECM. The relay and heater circuits are fine. This is not my problem.

 

[mwilson]

Bob4x4, I'm an experienced commercial/industrial electrician. I've read through Mopar's service manual and schematic. While the heaters are supplied by the batteries directly, the relay coils are controlled by the ECM. The relay and heater circuits are fine. This is not my problem.

Maybe the ambient temp has to be much colder before the ECM will activate the second one???



Don't discount Bob's battery suggestion, these trucks do some wierd things with a bad battery in the equation.



Mike.

 

[Bob4x4]

My apologies I was going from memory on code #. I was thinking 2509. I can give you some more info when I get home I have never seen an ECM failure cause your code. Not to say it can't happen

 

[ajpulley]

Not a problem; I'd like to think I've been thorough and systematic before asking for help.

Even though the batteries are two years old, I've tested the batteries with a load induced, and checked voltages, voltage drops and resistances across everything. I took every cable on the battery posts, relay posts and terminals, and the grid heater posts and cleaned them, and applied a commercial De-Ox. According the Dodge's service manual, the ECM monitors the voltage drop across the system for the first 15 seconds of running. Apparently, the drop of one heater is outside the parameters it is programmed for... having a drop from two heaters doesn't produce a MIL.

From another post at DTR, someone said they've seen chafed wires under the right battery tray, and suggested I pull the right front wheel well liner. When time, weather and temperatures allow, I'll think I'll give that a try and see what ever there is or isn't to see.

 

[Bob4x4]

Possible Causes

INTAKE AIR HEATER OPEN

INTAKE AIR HEATER GROUND OPEN

OPEN BATTERY CABLE FROM INTAKE AIR HEATER RELAY

BATTERY CABLE OPEN

#1 INTAKE AIR HEATER RELAY

#2 INTAKE AIR HEATER RELAY

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

Go To 2



No

Replace the open Intake Air Heater.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)







2. INTAKE AIR HEATER GROUND OPEN



--------------------------------------------------------------------------------

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

Go To 3



No

Repair the open Intake Air heater ground or replace both heater gaskets with the proper conductive gaskets.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)







3. OPEN BATTERY CABLE FROM INTAKE AIR HEATER RELAY



--------------------------------------------------------------------------------

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

Go To 4



No

Repair The open or high resistance battery cable from the intake heater relay to heater.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)







4. BATTERY CABLE OPEN



--------------------------------------------------------------------------------

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

Go To 5



No

Replace the battery cable from the battery to the Intake Air Heater Relay.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)







5. #1 INTAKE AIR HEATER RELAY



--------------------------------------------------------------------------------

Disconnect the #1 intake air heater relay signal wire.

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

Go To 6



No

Replace #1 Intake Air Heater Relay.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)







6. #2 INTAKE AIR HEATER RELAY



--------------------------------------------------------------------------------

Disconnect the #2 intake air heater relay signal wire.

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

Refer to the INTERMITTENT CONDITION - DIESEL Symptom. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)



No

Replace #2 Intake Air Heater Relay.

Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

 

[Freebore]

I have a 2007 5. 9 and experienced the codes P2509 and P2609, only when the temperature dropped. Although battery power seemed good, they were 6 years old so I replaced them with the Diehard Platinums, cleaned every ground I could find in the engine compartment and P2509 has not shown up since. P2609 for the heater grid has not been as easy to eliminate, and my truck only has one relay, not two. Apparently they reduced it to a single relay at some point.



I replaced the fused wire and relay with a new ones and cleaned all the wiring connections. It will still throw a code now and then - maybe once in the last 3 weeks. I believe I read somewhere about software updates where some of these codes were actually false and a reflash will take care of it. I'm less concerned about it now and is more than likely a nuisance that a reflash will fix.