TBI SENSOR DIAGNOSTIC - HOW TO WITH A MULTIMETER:

[Yeti_Owner]

I'm actually shocked this isn't already here, but... I made this for a thread a couple of minutes ago, and wanted to add it as a separate thread. Here you go!

TPS:

You must be registered for see images attach

Backprobe with a high impedance voltmeter at TPS terminals A and B.
With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.
If the voltage is not as specified, either the wiring to the TPS or the ECM may be faulty. Correct any wiring or ECM faults before continuing 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.

Map

You must be registered for see images attach

Backprobe with a high impedance voltmeter at MAP sensor terminals A and C.
With the key ON and engine off, the voltmeter reading should be approximately 5.0 volts.
If the voltage is not as specified, either the wiring to the MAP sensor or the ECM may be faulty. Correct any wiring or ECM faults before continuing test.
Backprobe with the high impotence voltmeter at MAP sensor terminals B and A.
Verify that the sensor voltage is approximately 0.5 volts with the engine not running (at sea level).
Record MAP sensor voltage with the key ON and engine off.
Start the vehicle.
Verify that the sensor voltage is greater than 1.5 volts (above the recorded reading) at idle.
Verify that the sensor voltage increases to approximately 4.5. volts (above the recorded reading) at Wide Open Throttle (WOT).
If the sensor voltage is as specified, the sensor is functioning properly.
If the sensor voltage is not as specified, check the sensor and the sensor vacuum source for a leak or a restriction. If no leaks or restrictions are found, the sensor may be defective and should be replaced.

Coolant Temp Sensor:
(This has to be done off the truck)

You must be registered for see images attach

You must be registered for see images attach

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.

 

[grampadirt]

Some good info

Use T-pins to backprobe with,got mine at a local arts & crafts shop.

You must be registered for see images attach

 

[SRT41320]

What does back probe mean?

 

[heavyjunk]

sticky?
It would be nice to find this quickly when needed.

Backprobing....lets see if I can explain it without confusing myself and ya'll. Take a pin/paperclip etc and insert it into the weatherpack connector from the backside following the wire untill it makes a connection with the pole inside. Don't actually probe the wire, just push it into the connector parralell to it. If your unsure if you have connection, with truck off, disconnect the connector and check for continuity between the pole in the connector and the backprobe pin. Hope you can understand it LOL

 

[SRT41320]

Cool man , thanx

 

[Yeti_Owner]

Good luck out there!

 

[Yeti_Owner]

Bumpity-bump-age.

 

[94Sierra4x4]

I'll be the first to admit, this thread seems like a foreign language to me.

 

[Yeti_Owner]

Rebump

 

[95C1500]

On a 3 wire o2 sensor, do you probe the o2 + or the o2 sensor signal wire (blk)? I probed the signal wire and got no voltage reading at all. My shop manual says under the DTC Code 44 section (which is the code that popped up at one point) that if the temperature is not warm enough (600F), the sensor will show no voltage (open circuit). I'm wondering if that's the case here or if I probed the wrong wire.