Engine wouldn't reach normal temp

[KidWithAGT]

Have had my 95 GT back out on the road for a couple weeks now, seemed to be fine until today. Went for a ride after work but at some point I realized the temp gauge wasn't passing the N on normal. Been checking everything I can think of, coolant levels seem normal, no steaming or smoking, no smoke from the exhaust, engine was running fine. I didn't have any real way to measure but the engine did seem to be a bit cooler than usual so I don't think the sender/gauge is messed up. The only thing I've noticed so far is that any time I turn the key to on, the fan turns on. Even if the engine is off, the fan will turn on. I've waited for it to cool off and the fan still turns on as soon as the key is turned. Any ideas what would cause this? My only ideas are a messed up coolant temp sensor or a stuck closed fan relay. Soon as I get a chance in going to go poke around with a multimeter and see if I can find the problem that way, but I'd appreciate any help you all have to offer.

Edit 1: Tested the temp sensor and the CCRM with a multimeter. Seems like the temp sensor is good, was reading within a couple degrees of the right temperature based on a chart I found online. The fan relay does not seem to be stuck closed, although I'm not so sure I tested that correctly. I checked for continuity between pins 1-2 and 3-4 and found nothing, which according to the wiring diagram I found 1-2 are the outputs and 3-4 are the 12v inputs. Also ran a KOEO test, which did confirm the fan is stuck on the low setting and not the high setting, but didn't give any related codes. So I'm at a loss, it appears as if the ECU is intentionally telling the fan to turn on despite the temps being low.

 

[07GtS197]

I have ran into this when the ecu doesn’t get signal from the coolant temp sensor. I find it hard to believe though since it seems that both of your sensors are affected. What code specifically was thrown? Do you have an infrared thermometer to check the temp around the engine bay?

 

[95opal]

Have had my 95 GT back out on the road for a couple weeks now, seemed to be fine until today. Went for a ride after work but at some point I realized the temp gauge wasn't passing the N on normal. Been checking everything I can think of, coolant levels seem normal, no steaming or smoking, no smoke from the exhaust, engine was running fine. I didn't have any real way to measure but the engine did seem to be a bit cooler than usual so I don't think the sender/gauge is messed up. The only thing I've noticed so far is that any time I turn the key to on, the fan turns on. Even if the engine is off, the fan will turn on. I've waited for it to cool off and the fan still turns on as soon as the key is turned. Any ideas what would cause this? My only ideas are a messed up coolant temp sensor or a stuck closed fan relay. Soon as I get a chance in going to go poke around with a multimeter and see if I can find the problem that way, but I'd appreciate any help you all have to offer.

Edit 1: Tested the temp sensor and the CCRM with a multimeter. Seems like the temp sensor is good, was reading within a couple degrees of the right temperature based on a chart I found online. The fan relay does not seem to be stuck closed, although I'm not so sure I tested that correctly. I checked for continuity between pins 1-2 and 3-4 and found nothing, which according to the wiring diagram I found 1-2 are the outputs and 3-4 are the 12v inputs. Also ran a KOEO test, which did confirm the fan is stuck on the low setting and not the high setting, but didn't give any related codes. So I'm at a loss, it appears as if the ECU is intentionally telling the fan to turn on despite the temps being low.

First off the guage sensor has nothing to do with the ECU, CCRM or fan. The ECU gets it temp reading from the ECT. Normally a bad ECT will throw codes 21 and 54. If its stuck on low id be looking at bad ccrm wiring to and from fan and ECU. You can also test the ECT sensor to see if its bad i dout it is.

 

[KidWithAGT]

I do not have a thermometer unfortunately, I'll see about getting one though if I can. The code was 332, insufficient egr flow. I was thinking a similar thing about the sensor or it's wiring going bad, which might actually make sense considering it seems like the temp gauger hovers right around where the thermostat opens. I tested the temp sensor though and it doesn't appear to be broken, no idea how I'd test it's connection to the ecu.

 

[95opal]

I do not have a thermometer unfortunately, I'll see about getting one though if I can. The code was 332, insufficient egr flow. I was thinking a similar thing about the sensor or it's wiring going bad, which might actually make sense considering it seems like the temp gauger hovers right around where the thermostat opens. I tested the temp sensor though and it doesn't appear to be broken, no idea how I'd test it's connection to the ecu.

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

Voltages may be measured across the ECT/ACT by probing the connector from the rear. Use care in doing it so that you don't damage the wiring or connector.

Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms

 

[KidWithAGT]

ACT & ECT test data:

Use Pin 46 on the computer for ground for both ECT & ACT to get most accurate readings.

Pin 7 on the computer - ECT signal in. at 176 degrees F it should be .80 volts

Pin 25 on the computer - ACT signal in. at 50 degrees F it should be 3.5 volts. It is a good number if the ACT is mounted in the inlet airbox. If it is mounted in the lower intake manifold, the voltage readings will be lower because of the heat transfer.

Voltages may be measured across the ECT/ACT by probing the connector from the rear. Use care in doing it so that you don't damage the wiring or connector.

Here's the table :

68 degrees F = 3.02 v
86 degrees F = 2.62 v
104 degrees F = 2.16 v
122 degrees F = 1.72 v
140 degrees F = 1.35 v
158 degrees F = 1.04 v
176 degrees F = .80 v
194 degrees F = .61

Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.

Ohms measures at the computer with the computer disconnected, or at the sensor with the sensor disconnected.
50 degrees F = 58.75 K ohms
68 degrees F = 37.30 K ohms
86 degrees F = 27.27 K ohms
104 degrees F = 16.15 K ohms
122 degrees F = 10.97 K ohms
140 degrees F = 7.60 K ohms
158 degrees F = 5.37 K ohms
176 degrees F = 3.84 K ohms
194 degrees F = 2.80 K ohms

Thanks, I'll see if I can get some sort of thermometer to get an accurate reading next to the sensor, then test the sensor's reading from the ECU's connector.

 

[KidWithAGT]

Read from the ECM connector between pins 46 and 7 the sensor has a resistance of 14.25 K ohms, the engine is at 112 degrees F. Seems like the sensor is good and the wires are good. What should I check next?

 

[95opal]

Hmmmm
Try checking the CCRM
Have the car below 200*F and the AC off. Look for ground at CCRM Pin 17 when the fan is on (but it should not be). If there's no ground signal at Pin 17, look for 12 volts at CCRM Pin 14. If neither is present but your fan is on, check CCRM pins 1 and 2 for power. If no power, check CCRM pins 6 and 7 for power. The former is low speed and the latter is high speed. If Pins 14 and 17 are dead but either 1 and 2 or 6 and 7 have power, that suggests a latched relay inside the CCRM.
I would expect the fan to be running even with the car off it the relay was stuck. The ECM has a trip code that will turn in the low speed fan on when it cant verify ECT signal. Are you sure you tested the correct Sensor.

 

[KidWithAGT]

Yup, I know I tested the ECT, did it both from the ECM connector as well as from the ECT pins themselves, same reading. I've got the ccrm out and checked if either high or low side relays are stuck closed, they are not.
Also checked all the fuses under the hood and in the driver's footwell, all good.

 

[KidWithAGT]

So I checked and confirmed that the engine is running at about 185 degrees, which makes sense since the fan won't let it warm up past the thermostat opening. I have a 180 degree thermostat. I did also notice that I'm getting airbag code 24, and I can't find any information about what that code means or how to fix it. Also not sure if this is two separate problems.
Worst case scenario, if I can't find a way to make the fan stop running when it shouldn't, is 185 a bad temp to be running at? I suppose I could put a higher thermostat in, but that seems like the wrong way to fix this haha.

 

[rabbit2620]

So I checked and confirmed that the engine is running at about 185 degrees, which makes sense since the fan won't let it warm up past the thermostat opening. I have a 180 degree thermostat. I did also notice that I'm getting airbag code 24, and I can't find any information about what that code means or how to fix it. Also not sure if this is two separate problems.
Worst case scenario, if I can't find a way to make the fan stop running when it shouldn't, is 185 a bad temp to be running at? I suppose I could put a higher thermostat in, but that seems like the wrong way to fix this haha.

I just got a 94 GT that is doing the same thing. Did you ever find out why you temp gauge was not working?

 

[cobrajeff96]

Did you add any extra grounds in the recent past?

Any temp below overheating is a good temp, lol. It's just that the car won't run as efficient as if it were right at (or even slightly above) water's boiling point at ambient pressure. Not a big deal to run slightly cooler, just means less power.

 

[KidWithAGT]

It's not really a matter of power, it's about the lifespan of my engine. Reaching a high enough temperature is important for an engine to run with the least amount of wear. I'm not worried about the engine just blowing up or anything, but long term this isn't good.

 

[KidWithAGT]

I just got a 94 GT that is doing the same thing. Did you ever find out why you temp gauge was not working?

Also, no fix yet unfortunately. Working on getting a new ccrm to see if that helps, I'll let you know if it does.

 

[cobrajeff96]

It's not an extreme performance engine and the amount of any wear due to it not being at optimal temp is negligible. Key word: optimal.

 

[KidWithAGT]

Either way I'd really rather not leave these issues be, if I can fix it I'd rather it be fixed.

 

[ttocs]

start by testing the senders resistance and you should be able to find a place that would show that the temp should be for that resistance. Now the temp gauge sender sends that data to the ECU that then dumbs it down to not scare the driver. I saw this in person in phoenix when they were dyno tuning my car and the temp gauge showed around the M-A of normal but the motor was so hot that he said it was pulling timing out to try and cool it down. Shortly after that it developed a knock but again the gauge never did show anything that would be concerning.

If you have had the gauges out recently I would go there next. The harness connection in the back of the pod is not the best and the trace lines can lift and touch the one next to it and cause all kinds of strange problems.

 

[cobrajeff96]

Ideally, yes.

 

[KidWithAGT]

start by testing the senders resistance and you should be able to find a place that would show that the temp should be for that resistance. Now the temp gauge sender sends that data to the ECU that then dumbs it down to not scare the driver. I saw this in person in phoenix when they were dyno tuning my car and the temp gauge showed around the M-A of normal but the motor was so hot that he said it was pulling timing out to try and cool it down. Shortly after that it developed a knock but again the gauge never did show anything that would be concerning.

If you have had the gauges out recently I would go there next. The harness connection in the back of the pod is not the best and the trace lines can lift and touch the one next to it and cause all kinds of strange problems.

I've been checking temps with a thermometer to make sure it wasn't the gauge completely lying to me, and It's always around 185 when I check. Just replaced the temp sensor with a new one and they both test the same, as well as both fit with the charts I found online so I don't think either is broken. I haven't ever had the gauges out either. Also I'm pretty sure the temp gauge and ECU use separate sensors.

 

[07GtS197]

Why did you use an 180* thermostat? I don’t know what your combo consists of but that’s low for a street driven car.

When I had my blue 00 gt it had, what I was told, an 185* thermostat and a mishimoto 3 core radiator. Hottest it would get while street driving was about 200*. It was wayyy overkill for an NA, bolt on street car that saw some dd duty. If you have a similar combo I wouldn’t be surprised your coolant temp numbers are as low as they are.