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**Z Ya Later** · 10-14-2007, 10:20 AM

The PCM will turn the fans on if an SES condition is triggered, so the SES light is on and the fans are running, that's normal. First thing is to get the car scanned (if possible) to find out what's triggering the SES light. I'm assuming you swapped or installed a new coolant sensor into the radiator, right?

**SeanC** · 10-14-2007, 10:33 AM

Yeh, I took the old sensor off the radiator I pulled out and slipped it on the new radiator. I've been trying to think of ways I can try to get the car scanned, but I really cant drive it anywhere right now...

**Jeff_in_Atl** · 10-14-2007, 10:43 AM

You are going to have to get it scanned. The good thing is since you have a 1996 you can use an OBDII scanner which are getting pretty cheap. You really should invest in one. It will be the first tool you grab when something goes wrong.

Oh and FYI the low coolant sensor does not go through the PCM so it is not the problem. All it does is light the light on the dash when the coolant is low and when it quits working just to irritate you.

**Injuneer** · 10-14-2007, 10:54 AM

Check for coolant splashed on the OptiSpark distributor. Make sure the wires and the distributor are dried off. Pull the plug wires, coil wire and Opti harness connector, and make sure the wires and terminals are not wet or corroded. Getting the distributor wet in an LT1 can cause the problem you are experiencing. Whenever you work on the coolant system, pack the area of the OptiSpark with rags to prevent it from getting wet.

There's also the possibility you knocked a wire off a sensor, like the coolant temp sensor in the water pump housing. That will cause an SES light, constant fans and hard starting.

But, as mentioned, scan it for codes. You can get an OBD-II code reader for $50 at Harbor freight. Spend a little more, and you can get an OBD-II code reader + scanner, that will prove even better in tracking down problems.

**SeanC** · 10-14-2007, 01:29 PM

Some progress! After really taking a good look through all the wires and sensors, I found out that my engine coolant temperature sensor that is at the bottom of the water pump was unattached. I tried to reattach it, but realized that the plastic plug in was missing. I called up my local auto parts store and they have it on order for tomorrow. I pray that this fixes the problem!

Could someone explain why having the coolant temperature sensor unplugged/not working causes the car to barely start? Why does it start cold, and not when it's warmed up? Is it just because the computer senses something wrong?

Everyone's help is greatly appreciated. Thanks guys! I'll let you know if the problem is fixed once I get that part.

**Joe 1320** · 10-14-2007, 05:05 PM

Originally posted by SeanC

Some progress! After really taking a good look through all the wires and sensors, I found out that my engine coolant temperature sensor that is at the bottom of the water pump was unattached. I tried to reattach it, but realized that the plastic plug in was missing. I called up my local auto parts store and they have it on order for tomorrow. I pray that this fixes the problem!

Could someone explain why having the coolant temperature sensor unplugged/not working causes the car to barely start? Why does it start cold, and not when it's warmed up? Is it just because the computer senses something wrong?

Everyone's help is greatly appreciated. Thanks guys! I'll let you know if the problem is fixed once I get that part.

When the car is cold, the computer bypasses many of the sensors and runs the car based on pre-computed tables stored in memory. once the car is up to operating temperatures, the computer switches over to sensor readings. When that temperature reading is inconsistant with what everything else is reading the hard starting issue comes into play. The temperature sensor is an integral part of the fuel mixture end of the program.

**Z Ya Later** · 10-14-2007, 05:20 PM

Originally posted by Jeff 95 Z28

You are going to have to get it scanned. The good thing is since you have a 1996 you can use an OBDII scanner which are getting pretty cheap. You really should invest in one. It will be the first tool you grab when something goes wrong.

Oh and FYI the low coolant sensor does not go through the PCM so it is not the problem. All it does is light the light on the dash when the coolant is low and when it quits working just to irritate you.

Well I wasn't saying it would, just asking to make sure that was done. Sheesh

lol

And I'll second what was said about the coolant sensor on the WP. When I was buttoning up my Z a few months ago we test-fired it without the sensor hooked up. She started great the first time, took a lot after that. Hopefully this is the same issue for you.

**SeanC** · 10-16-2007, 03:23 PM

Alright guys, I finally was able to buy a new sensor. I tried plugging in the wiring harness and it doesn't fit! So, I was able to get a hold of a new wiring harness plug in and it fits into the sensor perfectly. My question is, is this just something where they stopped making the factory plug in that is on my car, and switched to a newer style plug (the newer plug I guess is a "weather pac" plug while the old one has no weather sealing at all)? I'm planning on just clipping off the old plug in on the wiring harness on my car and soldering on the new one. Does this sound good to you guys?

**Injuneer** · 10-16-2007, 05:40 PM

Are you still talking about the coolant level sensor?

If so, there are two different part #'s listed on Shoebox's website. Which one did you buy?

http://shbox.com/1/low_coolant.jpg

**SeanC** · 10-16-2007, 05:42 PM

No, i'm talking about the engine coolant temperature sensor that the ECU reads

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