timmy39120

I am starting this thread as a way to track my troubleshooting of my latest issue with my car (Ah the joys of have a 20 year old daily driver).

The patient: 1995 Z28 Convertible

Using Scan9495 (Many thanks to Gary Doug), here are my results:

DTC 27: Exhaust Gas Recirculation (EGR) vacuum control signal solenoid valve circuit
DTC 32: Exhaust Gas Recirculation (EGR)
DTC 67: A/C refrigerant pressure sensor circuit (pressure sensor or A/C clutch circuit problem)

Elect Faults tab shows EGR solenoid Open

Symptoms:

When I start the car, approximately 30 seconds later I get a Malfunction Indicator Lamp (MIL) lit AND my cooling fans come on.

I do own the PDF of the 1995 Chevrolet Camaro and Pontiac Firebird Service Manual Book 1 and the supplement.


Speculation: I have had some weird issues with my A/C since I have had the car. Last summer, the A/C would just "not work". I could shut the car down and restart and it would magically work. I do not know if it is related to this, but since this constant MIL has been on (A little over a week) the A/C works every time. I have had an EGR DTC (I forget the number) for a while, but the MIL would only light up if I ran low RPM's (say 60 mph in 6th gear) for a couple minutes. I suspect that I need to replace the EGR solenoid, but will wait until I have run more diagnostics.

Any comments are welcome.

Injuneer

DTC 27 indicates faulty wiring for the solenoid, or faulty solenoid.

DTC 32 indicates the PCM triggered the EGR system to test it, and did not see the expected change in manifold absolute pressure that would be caused by EGR flow. This could even be from a very low back-pressure exhaust system. If the solenoid is bad, there is no flow, so you could get both codes just from that.

Test the EGR solenoid resistance... I think it's supposed to be about 15-30 ohms. But you are looking for a dead short (0 ohms) or an open (infinite ohms).

Not sure what would trigger DTC 67 without going back to the manual. Faulty sensor, loose connector?

timmy39120

Per the manual:

DTC 67 will set when: The PCM does not detect an A/C refrigerent pressure change of more than 4 psi when the A/C clutch has been cycled to "OFF" for 10 seconds, then "ON" for 10 seconds.

Action Taken (PCM will default to): DTC 67 will be stored in the PCM memory but will not turn "ON" the Malfunction Indicator Lamp (MIL), A/C operation will be disabled.

My A/C currently works. I suspect it is a loose wire somewhere, I just have to get under the hood with my fluke and go to town. I appreciate the info on the solenoid. I imagine that your value of 15-30 ohms is based on the coil resistance. That number sure as heck isn't in the book. I like the idea of checking for open or short across the coil. Hopefully that will be it cause a new solenoid is cheap. I will test and post the value.

Thanks for the help.

I wish I could copy paste out of adobe but all I have is the reader.

Injuneer

Someone was looking for a value for the solenoid resistance, and I measured mine, but it was a long time ago. If you think about it, that would limit the current to 1 amp or less, which is no problem for the PCM driver.

timmy39120

Well, the solenoid measured 13.98 ohms. I believe that I have found the problem evidenced by this picture:



Any ideas on where to get a new connector? Looks like I have enough wire to splice some in and add the connector.

FYI: My splice is solder with heat shrink. Seems to be the most durable but as always, suggestions welcome (Heat may be an issue that close to the engine).

timmy39120

Update:

Thank you shbox for your part number list. the part is:

AC Delco part number: PT374
GM Part number: 12102747

Went on Amazon and ordered it. Will provide update when installed.

timmy39120

UPDATE:

I ordered the connector. When it came in, I went to install it and realized that I didn't have any heat shrink tubing the same color so I had to order that. I was able to remove the old connector, solder the new one in and heat shrink the solder points. I reset the DTC.

I no longer get the MIL coming on after 30 sec and the fans do not come on either. It works as it should; however, when I am driving on a nice long flat road at 60 mph in 6th gear, the MIL will come on and I get the following DTC:

DTC 32: Exhaust Gas Recirculation (EGR)

The car was doing this before I replaced the connector. I suspect that either the EGR valve is fouled or needs replacement. I will try and delve deeper into it this weekend.

shoebox

If the solenoid had been inoperable for a long time because of the connector, it is possible the valve has gotten stuck from not being moved in a while. EGR testing info from shbox.com.
It is also not uncommon to get an EGR code if you have a very free flowing exhaust. The lack of backpressure can cause this.