Engine/Transmission (1994 - 1998) Intake Grid Heater Throwing Code

[EBansberg]

Hey guys, I just got a Check Engine light today. I noticed the past day maybe two that in the morning the grid heater wasn't cycling. I know because the voltmeter hasn't been swinging back and forth like it has for a few weeks now since the cold weather hit. code is P1291 which describes as "No Temp Rise seen from intake heaters". Obviously they aren't working since I've noticed and PCM noticed. My question is where to start. I've been searching and looks like I should start checking wiring connections first. Then maybe check relays? it seems like the Temp sensor is OK based on comp and me agreeing. Where do I start and do I maybe need a new heating element? Thanks.

 

[Centeno1]

an idea

i havent done much automotive electrical but in a house first you hot check before you start buying new parts just a thought make sure your getting power there in and out then you will know if its the element or not if powers not getting there then its a relay..... i would think. just my . 02

 

[BV]

My FSM is at home but here ya go from memory.

Check for voltage at the relays on the drivers inner fender well. These are fed from the battery threw fuseable links which can open.



Then I would jump the relay (jumper the two big lugs) and check that the grid heaters are working - You can use a test light, volt meter or your hand to feel the heat. Test one at a time and don't leave it on more then about 10 seconds or it gets pretty hot inside.



If this checks out okay then I will need to reference the manual for the next step. I know that the intake air temp (AIT) sensor can be checked with an ohm meter but I highly doubt that is bad.

 

[tmmy]

grid problems

E i would say to check the coolant temp sensor out if the pcm doesnt see coolant temp below 40 degrees I think it wont activate the grids there is a resistance check for this if not see if the solinoids are sending power to the grid also if it isnt getting enough power it wont heat to proper temp mybe u have a high resistance problem from corrision on the solinoids try it and let me know

 

[EBansberg]

I'm going to check the solenoids right now. I know that it was working a few days ago and it was pretty much a one day works, next day doesn't so I wouldn't think corrosion would be the prob but I'm going to play with it right now. Let you know in a while what a find.

 

[EBansberg]

Well, it was sort of corrosion. The two smaller cables that run from the positive battery terminal were connected to the battery before and now they are not. The connector that holds those two wires together and then holds on the battery terminal had corroded and broken off so the two wires were connected together still but not connected to the battery. Simple I guess, just gotta get a new connector tomorrow and put it back together. Thanks for the help though.

 

[tmmy]

heat grid problem

no prob i hope it works out for u let me know Tmmy