Grid heater experiment.

[Grumpy8811]

I live in SWFLA, so the grid heater probably doesn't do much work but you also read people saying how disconnecting the grid heater relay will cause a CEL and others do have a concern about the grid heater bolt.

anyway, I thought to myself the only way the engine ECM would be able to tell the grid heater was disconnected would be if the control wiring to the grid heater mag switch was disonnected as I couldn't think of any way the grid heater circuit power supply would affect what the engine ECM could read, so I disconnected the main power supply at the Pass Side battery two weeks ago.. just to see what happens. Basically nothing happens except the grid heater becomes non functional.

I am happy to say my conclusion was correct.. no CEL.. as the engine ECM has no way to know if current is actually flowing thru the grid heater relay contacts.. basically you could call this a poor mans grid heater delete..

 

[AH64ID]

I live in SWFLA, so the grid heater probably doesn't do much work but you also read people saying how disconnecting the grid heater relay will cause a CEL and others do have a concern about the grid heater bolt.

anyway, I thought to myself the only way the engine ECM would be able to tell the grid heater was disconnected would be if the control wiring to the grid heater mag switch was disonnected as I couldn't think of any way the grid heater circuit power supply would affect what the engine ECM could read, so I disconnected the main power supply at the Pass Side battery two weeks ago.. just to see what happens. Basically nothing happens except the grid heater becomes non functional.

I am happy to say my conclusion was correct.. no CEL.. as the engine ECM has no way to know if current is actually flowing thru the grid heater relay contacts.. basically you could call this a poor mans grid heater delete..

View attachment 142435

How cold has it gotten for you? What year is your truck?

That’s where I had my grid heater disconnected on my ‘22, waiting for the new relay, and it would randomly throw codes on cool mornings. But when it was warm it never would.

If you leave the relay connected but connect the output cable to the heater it’s less likely to throw a code, at least that was the case on my ‘05. Never tried on the 4th gens as I just bypass it most starts but leave it connected.

 

[Grumpy8811]

How cold has it gotten for you? What year is your truck?

That’s where I had my grid heater disconnected on my ‘22, waiting for the new relay, and it would randomly throw codes on cool mornings. But when it was warm it never would.

If you leave the relay connected but connect the output cable to the heater it’s less likely to throw a code, at least that was the case on my ‘05. Never tried on the 4th gens as I just bypass it most starts but leave it connected.

2016 Ram 3500... it was 44F this morning... it started right up.. 40 is about the coldest it gets here and that isn't very often...

 

[AH64ID]

2016 Ram 3500... it was 44F this morning... it started right up.. 40 is about the coldest it gets here and that isn't very often...

Cummins states a grid heater isn’t needed above 10°F, above that Ram uses them for emissions.

I’ve started sub-zero multiple times without issue and a removed grid heater.

If you were to have a slew of 40° mornings I bet you’d get a CEL after a while, that’s what happened with mine. It never popped if I bypassed the WTS light but would pop if the full WTS cycle was waited on, which is why it normally popped for the wife or on remote start.

 

[p-Bar]

The grid heaters were designed for sub zero temperatures. My 04.5 would start on 30 f mornings without waiting for heater .

 

[Learjet]

That is where I disconnected mine, folded it back and zip tied to the wire to keep it out of the way.

 

[DFark]

How cold has it gotten for you? What year is your truck?

That’s where I had my grid heater disconnected on my ‘22, waiting for the new relay, and it would randomly throw codes on cool mornings. But when it was warm it never would.

If you leave the relay connected but connect the output cable to the heater it’s less likely to throw a code, at least that was the case on my ‘05. Never tried on the 4th gens as I just bypass it most starts but leave it connected.

Mine is also a 22. I was going to disconnect the lead going to the heater, at the solenoid, but leave power connected to the solenoid. Is this the correct way to avoid throwing codes?

 

[Grumpy8811]

Mine is also a 22. I was going to disconnect the lead going to the heater, at the solenoid, but leave power connected to the solenoid. Is this the correct way to avoid throwing codes?

there are 4 wires on the grid heater relay/mag switch. solenoid etc... the 2 small wires are going to be what the ECM controls, aka one is the control wire to the relay coil from the ECM and the other is the ground wire for the relay coil.. disconnecting either end of the large wires accomplishes the same thing electrically, rendering the heating element non functional.. difference in where you disconnect is I did it at the battery + end of things, so all of the wiring is disconnected from Batt+.. disconnecting at the grid heater itself means all of the system will be live when the grid heater relay is being controlled by the ECM but no current will flow to the grid heater itself.. realistically it shouldn't matter which end of the large wires you disconnect..

 

[Learjet]

I agree ^^^^ but, the easiest place is at the battery terminal...Like shown above.

 

[AH64ID]

I agree ^^^^ but, the easiest place is at the battery terminal...Like shown above.

But this will throw a code, so it’s only the easiest way if you can clear the code.

there are 4 wires on the grid heater relay/mag switch. solenoid etc... the 2 small wires are going to be what the ECM controls, aka one is the control wire to the relay coil from the ECM and the other is the ground wire for the relay coil.. disconnecting either end of the large wires accomplishes the same thing electrically, rendering the heating element non functional.. difference in where you disconnect is I did it at the battery + end of things, so all of the wiring is disconnected from Batt+.. disconnecting at the grid heater itself means all of the system will be live when the grid heater relay is being controlled by the ECM but no current will flow to the grid heater itself.. realistically it shouldn't matter which end of the large wires you disconnect..

Not on his 2022. There are three connections, a plug for control and the main in and main out.

I’ve never tried disconnecting the main output on my 2022, but on my 2005 that was the only way to prevent a CEL.

As mentioned above, disconnecting the main input at the battery will trip a CEL on my 2022.

This is the grid heater from my 2022, and the style that prompted more discussion of disconnection. If your truck has the older style then just leave it connected and bypass the WTS light. You’ll still get post heat but that’s not as bad for the batteries as pre-heat.

 

[Learjet]

Disconnected at battery....No code on my truck unless you wait to crank and let it pre-heat or use the remote start when it is cold. The code can be cleared with a code reader. I forgot once and it easily cleared with my Scangauge II that I have hooked up.

 

[AH64ID]

Disconnected at battery....No code on my truck unless you wait to crank and let it pre-heat or use the remote start when it is cold. The code can be cleared with a code reader. I forgot once and it easily cleared with my Scangauge II that I have hooked up.

It does clear easily, and generally only sets a CEL if you let the WTS complete but not always.

 

[johnmyster]

Mine has the CEL off, but the code is present (shadow code) anytime I hook up the scanner.

It must look for either voltage drop when the GH is activated, or manifold air temperature rise. On my truck it isn't seeing either, so it sets the code.

 

[AH64ID]

Mine has the CEL off, but the code is present (shadow code) anytime I hook up the scanner.

It must look for either voltage drop when the GH is activated, or manifold air temperature rise. On my truck it isn't seeing either, so it sets the code.

They also have a BMS and could be looking for an amp draw.

 

[Grumpy8811]

Mine has the CEL off, but the code is present (shadow code) anytime I hook up the scanner.

It must look for either voltage drop when the GH is activated, or manifold air temperature rise. On my truck it isn't seeing either, so it sets the code.

going on 3 weeks since I posted the original comment... yeah, mine has the pending code too.. which I suspect is because we had one cold day ( I'm in Southern Fl)