I tested the Ohms at the 2 pins of the sensor, with the connector removed. The engine temp was 70 F ( 21 C) and the ohms were 2,400. The chart says the ohms are supposed to be around 3,400 for this temp. Is this far off enough to warrant replacement ? Oh, another thing, the reference voltage into the CTS (measured at the terminal of the opened connector) is only 4.1, as opposed to the normal 5.0 Volts. Do I need to fix the 4.1 vs 5.0 problem, or might just changing the CTS help me out. The car is running way too rich.

Here is a temp / resistance chart I found :

Temp ... Ohms
212F ... 177
194F ... 241
176F ... 332
158F ... 467
140F ... 667
122F ... 973
113F ... 1188
104F ... 1459
95F .... 1802
86F .... 2238
77F .... 2796
68F .... 3520 <--- me 70F and 2,400 ohms 59F .... 4450 close enough ??
50F .... 5670
41F .... 7280
32F .... 9420
23F .... 12300
14F .... 16180
5F ...... 21450
-4F .... 28680
-22F .. 52700
-40F .. 100700


Thanks


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88 GTA 5.7 TPI Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

[This message has been edited by GTA88 (edited July 28, 2001).]

 

GTA,

First, you need to be sure the meter is correct. A fresh calibration might be helpful. Many mid-range and low-dollar DMMs aren't highly accurate, and even top-end meters require periodic calibration.

If you're sure the meter is calibrated and correct and you still only get 4.1VDC at the sensor, you need to repair that problem first. The 5VDC refernce voltage is used for a lot of ECM I/O and needs to be pretty close to 5.0 volts. That alone may solve the rich condition.

Another thing to ascertain is that the coolant was actually at 70°F when you metered the sensor. A meter out of calibration could cause the skewed reading, or the temperature at the sensor might actually have been a little colder than 70°. The sensor element also needs to be clean to be able to sense the temperature correctly, and a little system corrosion and scale can insulate the sensor enough to skew the reading that much.

If all is correct, and the sensor still reads low, replace it. A new CTS is only about fifteen bucks.

------------------
Later,
Vader
------------------
"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Incidentally, the chart is as follows:



------------------
Later,
Vader
------------------
"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Vader,
I am using a new cheap little analog multimeter. But I think it must be accurate because I am getting exactly 5.0 volts as the ref voltage to the TPS. I am testing the ref voltage at the connector for both the TPS and the CTS. The connectors are very clean inside.
There is a little corrosion deep inside the 'port' on the CTS itself, but the 2 pins look clean. I got the 2,400 by probing the 2 pins (at least I think it was the pins, as opposed to one pin, and the back of the 'port'. )

------------------
88 GTA 5.7 TPI Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

Vader,
I am using a new cheap little analog multimeter. But I think it must be accurate because I am getting exactly 5.0 volts as the ref voltage to the TPS. I am testing the ref voltage at the connector for both the TPS and the CTS. The connectors are very clean inside.
There is a little corrosion deep inside the 'port' on the CTS itself, but the 2 pins look clean. I got the 2,400 by probing the 2 pins (at least I think it was the pins, as opposed to one pin, and the back of the 'port'. )

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88 GTA 5.7 TPI Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

I think you found your problem. That corrosion deep down inside can be acting as a resistor. Granted, the terminals might be clean, but what good does a "good contact" do, if the contact can't get the proper voltage. If your TPS is getting 5V, then there must be a problem between your splice (S180) and the CTS (since they share the same wire from the ECM) and I think thats where its at.

I would also replace the CTS as cheap insurance, but as long as you are getting 4.1V at the sensor, a new one won't do squat.

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