2021 2500. Truck has 44,000 miles. Got cel 2509. I just replaced the batteries a few days before. It has the AB relay in it as the recall was done. The intake bolt does not have any play. I unhooked the relay as shown in this forum from the battery. I still get the cel. I have tried the 2 push the starter button. Still comes on. Seems to take about 15 seconds after the truck has started. Any suggestions? Relay gone bad? Thanks Dave
Ram Heavy Duty Forum
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Grid heater relay
- Thread starter Dave97
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CdnHO
Well-Known Member
Do not disconnect the control wires from the relay. Disconnect the cable coming from the battery to the relay.
CdnHO
Well-Known Member
I disconnected the battery cable to the relay before the recall. I was able to keep the check engine light off by double tapping the start button. If I wasn't fast enough it set a code sometimes. I just cleared the code each time it happened. Since I am usually in a warm climate, the grid heater icon seldom comes on so a single tap is all that is required. Are you in a cold climate?
Not really cold mid 40’s to 60 right now. I’ve done the 2 push. Even with the engine fully warm, go into a store for 5 min come out and withfoot on the brake, hit the button one and immediately the truck starts. Within about 15 sec I hear the error chime. Is the relay bad? Is the ecu looking for some voltage causing the error even with no power?
CdnHO
Well-Known Member
I an finding that below 60, that the heater grid count down will often show up. Obviously an emissions thing.
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Even with quick double taps the CEL would randomly set on my truck. It was annoying enough I bought and replaced the relay on my own since Ram was taking so long. I’ve never waited the full WTS cycle and don’t feel it’s needed as much as programmed so was fine without it hooked up for months, but also don’t like a CEL tripped even thou it’s easy to reset with my CTS3.
I believe it comes on for pre-heat anytime the intake manifold temp is below 66°F.
CdnHO
Well-Known Member
I wonder if one could hook something into the heater circuit to mimick the current draw of the grid and disconnect the actual grid. Would solve the killter bolt problem as well as the CEL. Assume the system uses the temp from the driver's side mirror sensor.
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A resistor may do the trick, if that’s what the truck is looking for. It could be looking for a rise in IAT.
The ambient temp sensor in the mirror appears to be one of the sensors used, alongside the IAT sensor in the intake manifold.
CdnHO
Well-Known Member
If it is using a sensor inside the intake manifold that idea probably won’t work
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I don’t know for sure on the CGI blocks, but intake temp manifold temp was the main sensor on all previous CR’s.
Update
Took the truck to the dealer. They confirmed the CEL light. They ordered a new relay and wiring harness. My truck was already updated to the AB relay. That didn’t fix it. They ordered and replaced the ECU. That fixed it. I’m grateful it was covered under warranty for smog. The retail cost of the ecu was $4;200.
I’m not sure if was a coincidence, this started a couple of days after I replaced the batteries. Is there something special that needs to be done with the ibs on the battery when changing them?
Took the truck to the dealer. They confirmed the CEL light. They ordered a new relay and wiring harness. My truck was already updated to the AB relay. That didn’t fix it. They ordered and replaced the ECU. That fixed it. I’m grateful it was covered under warranty for smog. The retail cost of the ecu was $4;200.
I’m not sure if was a coincidence, this started a couple of days after I replaced the batteries. Is there something special that needs to be done with the ibs on the battery when changing them?
I seem to recall someone on cumminsforum tried that and IIRC could never get it to work reliably without setting a CEL.
Upon further investigation under the hood I found that the dealer ran a “jumper” wire from the small 2 wire line into the relay on the passenger side around the firewall to the drivers side and tied into a main harness. Not really sure why they did this. It is almost like the trigger wire to the relay being bypassed on the harness