C15 terminal on ECM what do it control or feedback?
Thread Starter
Burning Brakes
Joined: Sep 2001
Posts: 1,147
Likes: 72
From: Sumter, SC
C15 terminal on ECM what do it control or feedback?
On my ECM diagram C15 is labeled "injector drive 2,4,6,8 B". If I measure voltage through it I can ground it out at the EGR temp sensor in the pipe. If I permanently ground that wire what would I effect? What I'm thinking is if I ground that wire I won't get a code 32 because the ECM will sense the circuit closed. By thinking the circuit is close during start up or warmed conditions when the EGR would not be functioning anyway, will that cause other systems controlled by the ECM to work differently?
What I've found is that I don't have enough backpressure "for some reason" to open the EGR. Since it never opens it never closes the ground on the switch thus a code 32. By permanently grounded the sensor it is telling the ECM that the switch is working but all the time, not just when the egr is open.
So back to my orginal question. What does this injector terminal C15 control or what other feedback is altered by the voltage reading on this terminal?
Thanks,
I know there are easier ways like a chip and I'm going to do that but I'm also curious now.
What I've found is that I don't have enough backpressure "for some reason" to open the EGR. Since it never opens it never closes the ground on the switch thus a code 32. By permanently grounded the sensor it is telling the ECM that the switch is working but all the time, not just when the egr is open.
So back to my orginal question. What does this injector terminal C15 control or what other feedback is altered by the voltage reading on this terminal?
Thanks,
I know there are easier ways like a chip and I'm going to do that but I'm also curious now.
Instructor
Joined: Dec 1999
Posts: 209
Likes: 0
Re: C15 terminal on ECM what do it control or feedback? (Curtis629)
Curtis629, I'll take a stab at what your asking, but first a couple of things... In my '86 Helm manual, C15 is the dark green wire that goes only to the EGR Temperature Sense switch. This switch is normally open (when cold) and closes (allows current to flow) when it gets hot enough. When you start the car and the water temp is cold, this switch must be open or else you'll get a Code 32.... Another item, the EGR valve is opened and closed by vacuum, not by exhaust back pressure. The ECM turns the EGR solenoid on and off which turns the vacuum on and off to the EGR valve. A thought, if the EGR switch is not getting hot enough it will also set a Code 32. Perhaps the EGR pipe has gotten clogged which is why the Code is getting set. This should also make your engine run a little rough.... just my $.02.
Thread Starter
Burning Brakes
Joined: Sep 2001
Posts: 1,147
Likes: 72
From: Sumter, SC
Re: C15 terminal on ECM what do it control or feedback? (fundriving)
Thanks fundriving but that's not what I've seen so far, at least sort of.
The EGR has 2 springs in it. The upper big spring is controlled by the motor vaccum only. The smaller spring that actully opens and closes the pintle to allow the gas to flow must be controlled by back pressure. I tested this by appling vaccum on a new one outside the engine. The other part about the switch is this. The switch must read a really high temp to reduce voltage a little temp like 200F won't even move it. The tube that it's in isn't blocked because I can manually open the valve and watch the temp on the tube rise thus showing flow. I'm learning alot more than I ever wanted to about these darn EGR's but still can't figure out why my stock car doesn't create enough backpressure to allow the 2 spring to open the blessed thing.
Thanks for replying , all are appreciated.
The EGR has 2 springs in it. The upper big spring is controlled by the motor vaccum only. The smaller spring that actully opens and closes the pintle to allow the gas to flow must be controlled by back pressure. I tested this by appling vaccum on a new one outside the engine. The other part about the switch is this. The switch must read a really high temp to reduce voltage a little temp like 200F won't even move it. The tube that it's in isn't blocked because I can manually open the valve and watch the temp on the tube rise thus showing flow. I'm learning alot more than I ever wanted to about these darn EGR's but still can't figure out why my stock car doesn't create enough backpressure to allow the 2 spring to open the blessed thing.
Thanks for replying , all are appreciated.
