Grid Heater

[AWay]

When my '06 was new, the grid heater never came on till it got damn cold. Now, let it get down to 50 degrees and the darn thing comes on.

 

[AABEN]

That is OK at leas you know it is working.

 

[p-Bar]

Mine comes on in So. Cal. on the coast ready to pull it out

 

[DaveHess]

Mine comes on anytime the ambient temperature is 66 degrees or less. I read that somewhere. I think it came from the service manual. Somewhere else I read that the overhead temperature is not the temperature the grid heater is turned on by.

 

[rbattelle]

Somewhere else I read that the overhead temperature is not the temperature the grid heater is turned on by.

This is quite true. The grid heater cycle is controlled by the intake air temperature, which often differs from the overhead.



Ryan

 

[AWeiman]

When my '06 was new, the grid heater never came on till it got damn cold. Now, let it get down to 50 degrees and the darn thing comes on.

our '06 is like that has to be pretty cold for them to come on, and the truck has to sit for quite a long time in the cold for them to come back on again after it has been running.

certainly not like my '01. any there major differences between the two grid heater systems? wait to start light always comes on in the '01, as stated above not the case in the '06.

 

[JBonpua]

I believe the GH is also part of the emission control. Mine is MIA and replace with a Winspeed spacer. Don't need it here in Sacramento.

 

[Bill Weber]

I don't believe rbattelle is correct. If the heater is controlled by incoming air temp it would never quit cycling in cold temps. Park my warm truck for 5 min in 55F weather and the heater is cycling when I start it. Don't know what the controller is looking at but it sure isn't engine temp.

Replaced the heater with a spacer, S. Texas isn't usually cold, and cruising boost went UP 1 - 1. 5#.



Bill

 

[rbattelle]

I don't believe rbattelle is correct.

Well, you might well be right - it wouldn't be the first time I was completely wrong on something. The Powertrain Diagnostic Manual, page 8 reads:

The ECM monitors the intake air temperature signal.

In my opinion, the intake air temperature signal comes from the intake air temperature sensor, as opposed to the ambient temperature sensor, described in the service manual, page 8M-10:

Ambient air temperature is monitored by the overhead console. The FCM receives a hard wired input from the ambient temperature sensor.

Attached is the relevant wiring diagram for the ambient temperature sensor. In my opinion, this diagram shows the sensor is connected directly to the FCM. Furthermore, the ambient temperature sensor is the only air temperature sensor wired to the FCM.

Also attached is the relevant wiring diagram for the intake air temperature sensor. Again, in my opinion, the sensor is wired directly to the ECM. Furthermore, the IAT sensor is the only air temperature sensor wired to the ECM.

As we know, the intake temperature sensor doesn't read the same as the ambient temperature sensor, as evidenced by the difference in readings when observing the relevant data stream.

Regarding the grid heaters running continuously if the input data is coming from the intake sensor, I'm not clear on why this would be the case. The way I read it, the PDM indicates the ECM is programmed to operate the heaters according to a strict temporal schedule based upon the intake temperature reading at startup (the ECT sensor is not part of this programming, as you observe). Refer to page 8 in the PDM for the relevant schedules.

I apologize if I'm wrong about all of this. It's based on my perhaps-flawed understanding of the PDR, FSM, and wiring diagrams.

Ryan

 

[AH64ID]

I don't believe rbattelle is correct. If the heater is controlled by incoming air temp it would never quit cycling in cold temps. Park my warm truck for 5 min in 55F weather and the heater is cycling when I start it. Don't know what the controller is looking at but it sure isn't engine temp.

Replaced the heater with a spacer, S. Texas isn't usually cold, and cruising boost went UP 1 - 1. 5#.



Bill

It looks at a combo of manifold temp, intake air temp, and engine temp. 66* is the manifold/intake air temp cutoff. Engine temp determines the length it runs (per cycle, not overall time), and I don't think it plays a huge role in choosing if it cycles.



Where are you reading boost? I assume in the manifold?





Also the WTS light only works when the engine temp is cold, but the grid heater still works. So don't confuse WTS operation with GH operation.