I had my mechanic plug into my 92 305 and it read.. something about the egr, and temp sensor was "shorting out". He said he was confused about what he read. Any help would be greatly appreciated..

 

Well that is as little information as humanly possible.

You do not mechanic to read codes on your third gen - all you need is to find ALDL connector and with ignition "ON" and engine "NOT RUNNING" use a jumper (paper clip) and connect terminal "B" to terminal "A". Terminal "A" is the ground connection.

The ECM will cause the "Service Engine Soon" light to flash Code 12, indicating that the ECM diagnostics are working. Code 12 will flash three (3) times, followed by any other trouble codes stored in memory. Each additional code will flash three (3) times, starting with the lowest code, and then start over again with Code 12. If there are no other codes, Code 12 will flash until the diagnostic jumper is disconnected or the engine is started.

1) Temp sensor shorting out would result in code 14 - CTS low (yellow wire is being pulled to ground, or CTS sensor shorted)

2) EGR faults typically result in code 32, but I would resolve CTS first before chasing EGR.

//RF

 

This should help http://www.troublecodes.net/GM/

 

I had an employee do the paperclip thing, but he couldn't get it to work. I went ahead and replaced the temp sensor. It's been running good, but I still get the check engine light coming on. The meter the other guy used was supposed to be for older computer controlled engines. Is there an egr sensor, or would it be the egr???

 

IFRC on '92 EGR valve is located on passenger side of intake manifold next to # 6 cylinder intake runner. On high mileage cars EGR passage may have accumulated carbon build up and that prevents adequate exhaust gas flow. There is no EGR flow or temperature sensor. ECM verifies EGR functionality indirectly by looking for MAP voltage change when EGR is commanded.
Another common fault is with EGR itself - diaphragm fails to keep vacuum. Use Mitivac hand held vacuum test pump to verify diaphragm integrity. On rare occasions EGR control solenoid that controls amount of vacuum (and duty cycle) of EGR fails.

As usual verify that all vacuum tubes are in good shape.

The clip trick should work - unless your co-worker did not jump correct set of pins.
//RF

 

That was a lot of good info. I have a 305 just in case you thought I had a six. I was told there were 3 different temp sensors. One for the computer, one for the fan, and one for the gauge. I replaced the temp sensor that was located near the thermostat. I wanna know what your take is on this.

 

Actually you have two temperature sensors and one temperature switch. The temperature sensor that screws into the head is used to provide instrument cluster indicator. The one by the thermostat (aka CTS) is used by ECM to determine engine coolant temperature. CTS has a two wire connector with one yellow and the other wire being black. Temperature switch has temperature hysteresis to prevent electric cooling fans from being cycled to often.
When I referred to #6 cylinder intake runner I basicly tried to indicate relative postion of EGR on intake manifold. As you know passenger side cylinders on SBC are even numbered e.g. 2, 4, 6, 8 with eight being a tough one to get to in the back.

//RF

 

Ok. The one I replaced is the one that sends info to the chip. Next spring, I need to assess the EGR, and the vac hoses. It seems to run smoother, and starts cold smoother since I replaced the temp sensor. I still get a check engine light occasionally, but no hicup. I did clear the codes since the sensor replacement. I did hook a switch (ground) to the temp switch so I can run the fan at will. I have a 180 thermostat, and I don't usually let it get any hotter.