CTS Wiring to where??

!S10-Dave · 10-24-2009, 11:56 PM

Ok I got the newer engine put in the truck and it runs great but the Coolant Temperature Sensor isn't working at all. Mainly because there is no wire or connector for it anywhere. I bought a connector for it but I don't have a clue where to hook up the wires for it to work right. It has one black wire and one yellow wire. I suppose the yellow is my hot wire and the black is ground. Anyone have any ideas to where these wires go?? Im thinking if this is hooked up right, the truck will run better and idle better. Thanks for any help

lesterl · 10-25-2009, 03:01 PM

First off, what did you put the motor in? Second, what year was the Motor?

How does it run without the CTS? Where did your original hook up?

!S10-Dave · 10-25-2009, 04:01 PM

I put it in a 91 s10 4x4, its a 4.3 liter, came out of a 91 s10 2wd. It runs great actually but there was never a connector for the CTS on the old engine or the engine harness itself. So im not able to put it on this newer engine. I just need to know where to hook it up so its functional.

lesterl · 10-25-2009, 10:34 PM

It should have had a CTS. Look near the water neck on the intake manifold.

A CTS will usually have 2 wires, yellow and black, the dash sender will usually have 1 wire (green).

!S10-Dave · 10-26-2009, 01:14 AM

Nope. The old engine that I took out had the Sensor snapped in half with no wire attached. So I will have to go check it out later.

**far2grumpy** · 10-26-2009, 10:58 AM

Quote: Originally Posted by !S10-Dave

I put it in a 91 s10 4x4, its a 4.3 liter, came out of a 91 s10 2wd. It runs great actually but there was never a connector for the CTS on the old engine or the engine harness itself. So im not able to put it on this newer engine. I just need to know where to hook it up so its functional.

Dave ... I located 1988-1992 wiring diagrams on-line at our local library. Pages are too large to post according to forum limits. I can email if you PM address.

If the diagrams are correct, 4.3 for these years have separate coolant temp sensor (CTS) and water temp sender.

The CTS high side is a yellow wire connected to ECM C10, and low side is purple, connected to low side of MAP and then to ECM D2.

The lead from water temp sender to gauge is dark green (per lesterl).

!S10-Dave · 10-26-2009, 05:55 PM

I realized that when I went and looked at it today that there was something different than what I was looking at. The CTS is connected on my engine right now so it is in working order as far as I know.

Thanks for pointing that out guys. So what is on the low side is the water temp sender, correct? Should I be worried about leaving that disconnected or should I have it connected to the ECM?

**far2grumpy** · 10-26-2009, 10:44 PM

Quote: Originally Posted by !S10-Dave

I realized that when I went and looked at it today that there was something different than what I was looking at. The CTS is connected on my engine right now so it is in working order as far as I know.

Thanks for pointing that out guys. So what is on the low side is the water temp sender, correct? Should I be worried about leaving that disconnected or should I have it connected to the ECM?

I'm going from memory here but most old senders (water temp, oil pressure, etc) are single point ... you screw them into an engine part which creates the ground path.

There's another ... single lead ... which goes to the needle movement input of the meter (gauge).

There could be two other wires connected to gauge - one to +12 and the other to ground.

lesterl · 10-26-2009, 10:46 PM

Dash guages have a single input wire - 12v system.

ECM inputs have 2 wires - 5v system.

Guages will usually have a 12v and a ground lead, the sender will pull the 12v to ground thru the sender into the block.

10-24-2009, 11:56 PM	#1
!S10-Dave 91' S10 4x4/89' Camaro RS Age: 22 Join Date: Aug 2009 Posts: 18 Location: Mid Michigan User is: OffLine	CTS Wiring to where?? Ok I got the newer engine put in the truck and it runs great but the Coolant Temperature Sensor isn't working at all. Mainly because there is no wire or connector for it anywhere. I bought a connector for it but I don't have a clue where to hook up the wires for it to work right. It has one black wire and one yellow wire. I suppose the yellow is my hot wire and the black is ground. Anyone have any ideas to where these wires go?? Im thinking if this is hooked up right, the truck will run better and idle better. Thanks for any help
	[Reply w/Quote]

10-25-2009, 03:01 PM	#2
lesterl Wire Splicin Fool :-) Age: 30 Join Date: May 2008 Posts: 5,064 Location: Harrisonville, MO User is: OffLine	Re: CTS Wiring to where?? First off, what did you put the motor in? Second, what year was the Motor? How does it run without the CTS? Where did your original hook up?
	[Reply w/Quote]

10-25-2009, 04:01 PM	#3
!S10-Dave 91' S10 4x4/89' Camaro RS Age: 22 Join Date: Aug 2009 Posts: 18 Location: Mid Michigan User is: OffLine	Re: CTS Wiring to where?? I put it in a 91 s10 4x4, its a 4.3 liter, came out of a 91 s10 2wd. It runs great actually but there was never a connector for the CTS on the old engine or the engine harness itself. So im not able to put it on this newer engine. I just need to know where to hook it up so its functional.
	[Reply w/Quote]

10-25-2009, 10:34 PM	#4
lesterl Wire Splicin Fool :-) Age: 30 Join Date: May 2008 Posts: 5,064 Location: Harrisonville, MO User is: OffLine	Re: CTS Wiring to where?? It should have had a CTS. Look near the water neck on the intake manifold. A CTS will usually have 2 wires, yellow and black, the dash sender will usually have 1 wire (green).
	[Reply w/Quote]

10-26-2009, 01:14 AM	#5
!S10-Dave 91' S10 4x4/89' Camaro RS Age: 22 Join Date: Aug 2009 Posts: 18 Location: Mid Michigan User is: OffLine	Re: CTS Wiring to where?? Nope. The old engine that I took out had the Sensor snapped in half with no wire attached. So I will have to go check it out later.
	[Reply w/Quote]

10-26-2009, 10:58 AM	#6
far2grumpy Somewhat cynical Join Date: Sep 2009 Posts: 136 Location: Cedar Rapids, IA User is: OffLine	Re: CTS Wiring to where?? Quote: Originally Posted by !S10-Dave I put it in a 91 s10 4x4, its a 4.3 liter, came out of a 91 s10 2wd. It runs great actually but there was never a connector for the CTS on the old engine or the engine harness itself. So im not able to put it on this newer engine. I just need to know where to hook it up so its functional. Dave ... I located 1988-1992 wiring diagrams on-line at our local library. Pages are too large to post according to forum limits. I can email if you PM address. If the diagrams are correct, 4.3 for these years have separate coolant temp sensor (CTS) and water temp sender. The CTS high side is a yellow wire connected to ECM C10, and low side is purple, connected to low side of MAP and then to ECM D2. The lead from water temp sender to gauge is dark green (per lesterl).
	[Reply w/Quote]

10-26-2009, 05:55 PM	#7
!S10-Dave 91' S10 4x4/89' Camaro RS Age: 22 Join Date: Aug 2009 Posts: 18 Location: Mid Michigan User is: OffLine	Re: CTS Wiring to where?? I realized that when I went and looked at it today that there was something different than what I was looking at. The CTS is connected on my engine right now so it is in working order as far as I know. Thanks for pointing that out guys. So what is on the low side is the water temp sender, correct? Should I be worried about leaving that disconnected or should I have it connected to the ECM?
	[Reply w/Quote]

10-26-2009, 10:44 PM	#8
far2grumpy Somewhat cynical Join Date: Sep 2009 Posts: 136 Location: Cedar Rapids, IA User is: OffLine	Re: CTS Wiring to where?? Quote: Originally Posted by !S10-Dave I realized that when I went and looked at it today that there was something different than what I was looking at. The CTS is connected on my engine right now so it is in working order as far as I know. Thanks for pointing that out guys. So what is on the low side is the water temp sender, correct? Should I be worried about leaving that disconnected or should I have it connected to the ECM? I'm going from memory here but most old senders (water temp, oil pressure, etc) are single point ... you screw them into an engine part which creates the ground path. There's another ... single lead ... which goes to the needle movement input of the meter (gauge). There could be two other wires connected to gauge - one to +12 and the other to ground.
	[Reply w/Quote]

10-26-2009, 10:46 PM	#9
lesterl Wire Splicin Fool :-) Age: 30 Join Date: May 2008 Posts: 5,064 Location: Harrisonville, MO User is: OffLine	Re: CTS Wiring to where?? Dash guages have a single input wire - 12v system. ECM inputs have 2 wires - 5v system. Guages will usually have a 12v and a ground lead, the sender will pull the 12v to ground thru the sender into the block.
	[Reply w/Quote]