TBI SENSOR DIAGNOSTIC - HOW TO WITH A MULTIMETER:

[PlayingWithTBI]

You should have 2 white wires and 1 black? The white ones are for the heater, the black is your signal wire...

 

[95C1500]

You should have 2 white wires and 1 black? The white ones are for the heater, the black is your signal wire...

So I checked the correct wire it sounds like. I'll try again with a better ground and see if I just wasn't making a good connection.

 

[anson1342]

Should the map sensor increase when idling on the a and c terminals or the a and b terminals?

 

[Schurkey]

Backprobe with a high impedance voltmeter

Let's define "high impedance".

GM used to specify a minimum of 10 Megohm input impedance. Higher is better. On extremely low-amperage circuits like the O2 sensor, you can actually see a voltage difference when testing with a 10 Megohm unit vs. a 20 Megohm meter. The higher the input impedance, the higher (and more-accurate) the voltage readout.

There was a time, a bazillion years ago, when 10 Megohm input impedance (or greater) on a voltmeter was kinda rare. Not so much any more.

at TPS terminals A and B.
With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.

This tests the computer power supply, the computer ground, and the two wires along with whatever connectors are in that circuit. Valid test.

Backprobe with a high impedance voltmeter at terminals C and B.
With the key ON and engine off and the throttle closed, the TPS voltage should be approximately 0.5-1.2 volts.
Verify that the TPS voltage increases or decreases smoothly as the throttle is opened or closed. Make sure to open and close the throttle very slowly in order to detect any abnormalities in the TPS voltage reading.
If the sensor voltage is not as specified, replace the sensor.

Valid test for the SENSOR if performed carefully. NOT a valid test of the signal wire going back to the computer. In other words, the SENSOR can be totally fine...but the computer may not get the signal, may not get the signal correctly, or may have an internal fault where it can't process the signal.

Testing with a scan tool is the superior method, as it verifies that the computer is receiving the signal and can "understand" it. Moreover, a person can verify ALL the sensors with a scan tool in the time it takes to check one or two with a multimeter. (And with zero risk of damaging the weather-tight seals around the wires in the connector bodies.)

Backprobe with the high impotence voltmeter

An impotent voltmeter will be unable to swallow Via-gra or Cialis. Probably requires surgery.

Really? The name of a prescription medication is censored on this forum?

O2 Sensor:

Start the engine and bring it to normal operating temperature, then run the engine above 1200 rpm for two minutes.

Backprobe with a high impedance averaging voltmeter (set to the DC voltage scale) between the oxygen sensor (02S) and battery ground.

Verify that the 02S voltage fluctuates rapidly between 0.40-0.60 volts.

If the 02S voltage is stabilized at the middle of the specified range (approximately 0.45-0.55 volts) or if the 02S voltage fluctuates very slowly between the specified range (02S signal crosses 0.5 volts less than 5 times in ten seconds), the 02S may be faulty.

Ideally, you'd see a greater voltage swing than just 0.40--0.60 volts. I'd hope to see at least some voltage between 0.2--0.8, and greater swing than that would be nice.

As said--faster (more) cross-counts is better.