C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Problem throwing the same code... I give up

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Old Jul 22, 2016 | 01:28 AM
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Default Problem throwing the same code... I give up

First off the car a 1996 CE LT4 starts instantly and runs and drives perfect but the SES has been on throwing a P0118 code. So I replace the sensor in the water pump and clear the code. 5min later the same code makes the SES light come on again.

Before I replaced the sensor and after the car won't start when warm or hot unless I put the gas pedal to the floor and it starts idles at 2200rpm and slowing comes down.

Does this sound like the ICM? I don't understand I replaced the sensor so why is it still throwing the same code.

Oh and the harness is fine and it's getting 5.3vDC.

I'm just out of ideas other than replacing the ICM but wanted your opinion before I spend $100.
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Old Jul 22, 2016 | 12:28 PM
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No one?
Looks like I'll play the guessing game now.
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Old Jul 22, 2016 | 12:50 PM
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You already did play the guessing game by throwing a sensor at it. That didn't work. There is more to diagnosis than replacing the sensor that an DTC is referencing.

Test (ohm) the sensor. Test the harness for continuity from the sensor to the ECM. Report back.


.

Last edited by Tom400CFI; Jul 22, 2016 at 12:52 PM.
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Old Jul 22, 2016 | 02:39 PM
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Originally Posted by Tom400CFI
You already did play the guessing game by throwing a sensor at it. That didn't work. There is more to diagnosis than replacing the sensor that an DTC is referencing.

Test (ohm) the sensor. Test the harness for continuity from the sensor to the ECM. Report back.


.
tom 400 is right,, i had the same problem and my problem was 2 fold, new sensor was not good enough,,, and a loose connection on the connector to the sensor . do a scan if you have a -400 then you have an open, of course your car would run crappy or hard start..
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Old Jul 22, 2016 | 04:56 PM
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Tested the harness I have the 5volts and continuity? But when I have my scanner plugged in it shows ECT -40 degrees so I haven't a clue what's that about. And the gauge is spot on its not like the gauge is acting crazy.

Before I put this one in I checked the ohms at room temperature then put the tip in simmering water and checked again and they both correlated for a graph I saw on here once.

The harness terminals look like new so I know it's not a bad connection.

It's just the live data thing that has me stumped... does anyone know if they will pass/fail a nys inspection just for this one stupid code.
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Old Jul 22, 2016 | 05:24 PM
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I have another question : are you looking for continuity between one side of the harness to the body of the ecm or ground or a certain pin on the ecm?
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Old Jul 22, 2016 | 05:27 PM
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The sensor is good I had it at different Temps and checked the ohms and it correlated with a graph I saw on here.
Should I get a new harness and cut the old one out and splice it in?
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Old Jul 22, 2016 | 05:28 PM
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Oh one thing that confuses me is on my live data screen when the gauge reads 60-190 degreed the ECT on live data says -40 degrees
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Old Jul 22, 2016 | 05:57 PM
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Originally Posted by Lt4-396
Oh one thing that confuses me is on my live data screen when the gauge reads 60-190 degreed the ECT on live data says -40 degrees
Doesn't your car have the gauges button on the Driver Information Center?

If so you press that button until you see temperature of the Engine Coolant Temperature sensor displayed in the Dash Cluster LCD.

The dash temperature analog gauge uses a different sender.

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Old Jul 22, 2016 | 05:59 PM
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Check the harness

That sensor tends to get hit when the belt is changed.
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Old Jul 22, 2016 | 06:04 PM
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Yes I know that sender is for the digital gauge and the gauge works perfect, so wouldn't that mean the harness and everything else is good?
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Old Jul 22, 2016 | 06:09 PM
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thinking an intermittent connection
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Old Jul 22, 2016 | 06:22 PM
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So you think i should get a new harness cut the old one out and splice and solder the new one in?
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Old Jul 22, 2016 | 06:24 PM
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I just dont understand how the gauge can work perfectly but its still throwing the p0118 code. Also i dont know if this means anything but the digital gauge doesnt go past 193 degrees.
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Old Jul 22, 2016 | 06:31 PM
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Originally Posted by Lt4-396
So you think i should get a new harness cut the old one out and splice and solder the new one in?
I'd check the connectors, may just need a cleaning

Put a meter on it, jiggle the wires, see if it changes.
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Old Jul 22, 2016 | 06:40 PM
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The harness connectors are nice and shiny with a tiny bit of di electric grease on it. I tested the one side and got the 5v the othe side do i just test the continuity from the harness to ground from the harness to the ecm ”box” or a certain pin when you remove the ecm harness?
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Old Jul 22, 2016 | 06:56 PM
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I'm sure there is, that's where my knowledge ends

Careful on the ECM connector, they get fragile with age
One of my clips has already broken from getting brittle.
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To Problem throwing the same code... I give up

Old Jul 22, 2016 | 07:51 PM
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Thanks for everything. Alot of people have been saying the harness may be bad but if that was true wouldnt the temp gauge not work. The fact that the temp gauge works to me means the signal is making it back to the ecm.
I wonder if the ecm could somehow be bad.
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Old Jul 22, 2016 | 10:42 PM
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Originally Posted by Lt4-396
Thanks for everything. Alot of people have been saying the harness may be bad but if that was true wouldnt the temp gauge not work. The fact that the temp gauge works to me means the signal is making it back to the ecm.
I wonder if the ecm could somehow be bad.
The analog temperature gauge uses a CTS (Coolant Temperature Sensor) in the passenger side head. The ECM uses a CTS in the water pump. The ECM is the source for the digital temperature display.
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Old Jul 22, 2016 | 11:35 PM
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Yes I know all of that, it'sy fault but anytime I said gauge I meant the digital gauge, it has never been out of whack once. My buddy has a 1996 lt1 corvette I think I'm going to try switching ecm's and see what happens.
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