Questions and Answers

Chevrolet Corvette DTC 32 Q. Dear Vince, A little advice would be greatly appreciated. I recently purchased a 1990 Chevrolet Corvette serial number 1G1YY2 382L 510257 with a computer problem. The Computer service number is 16198260. Vehicle has: Climate control air conditioning 6 speed transmission Cruise control 50,400 miles Tuned port fuel injection Rack and pinion steering

THE PROBLEM:
At Idle or under 2,000 RPM no codes appear. If the vehicle is driven on the highway at a speed where the EGR system can become active some time between ten minutes and one hour the Service Engine Light will be turned on. This symptom is the same even if the car is shut of and the code cleared.

ATTEMPTED REMEDY:

• I scanned the unit utilizing a SnapOn scanner. CODE 32 EGR Problem was activate.
• I cleared the code and prepared to test the EGR system.
• First confirmed that there was 10 inches of Hg vacuum at 2,000 RPM.
• Hooked vacuum pump to EGR solenoid and confirmed vacuum would bleed off with out test mode active then activated test and EGR solenoid held 10 inches of vacuum.
• Unhooked EGR VAlve from solenoid connected vacuum pump and applied 16 inches Hg to EGR valve. Confirmed with a mirror that Diaphragm was moving.
• Had the car turned over and vacuum bled off through pintle port as per spec.
• Checked solenoid resistance and got 34.5 ohms. Should be okay to this point.
• Confirmed the power source was at the EGR solenoid, and confirmed the gray wire that ran back to the computer had no open. Activated test mode and test light bridged across terminal end lit up. ECM working
• Checked vacuum on other side of ported vacuum source, "evaporator system."
• Repaired leak and it then held 20 inches HG.
• Test drove car code 32 appeared as before.
• Considered the other possibilities and checked the voltage output of the Map sensor. 3.5 volts at 3500 feet above sea level output was 89 kpa = 12.9 psi
• Mitchell manual indicated a map sensor may be off calibration enough not to see the manifold pressure change when the EGR opened
• Purchase and installed map sensor. Same symptom.
• Tested resistance on all solenoids connected to Pink Blk stripe circuit. 30 ohms or greater.
• Can't find the vehicle speed sensor buffer or the ride control solenoid on this circuit. but tested everything in this solenoid grouping ILC, AIR diverter control and air control. All associated solenoids okay.
• Decided at this time I had too much money and replaced the EGR Valve, EGR solenoid, all vacuum lines, thermostat, and the MAT sensor while the plenum was off. No change.
• After finding out I still had too much money I replaced the ECM.

Test drove car and vehicle operated for 2 hours then flagged code 32. Almost success. My next step is to power down the electrical system, remove every connector, one at a time, from the plug in block and re-crimp the connectors at the ECM plug to ensure a good connection.

I don't think the solution is to remove the Service Engine Light but what am I missing? I am not a mechanic just a car nut that does this for fun. BUT this is personal now and I will not stop until I have found this glitch. Any advice is appreciated.

Lee

A. I'm not positive but isn't there a diagnostic switch in this EGR system? A little single wire switch or sensor that is in the EGR port somewhere? Maybe it's bad. I'm trying to picture this setup in my head and can see this switch on it. I could be wrong but sounds like you've covered everything else. It's a fairly simple system until you get a problem that doesn't go away.

Also thinking that maybe the scanner is not compatible with this car. I know the GM scanner needed a special adapter to hook on Tech 1 to access a Corvette ALDL. One other thought, maybe the EGR "system" is okay and there is no exhaust gases flowing through the valve due to clogged ports?

I would go to a Chevy dealer and gat a copy of this TSB. It may help you troubleshoot the problem.

9216chevy10
Number: 91-327-6E
Section: 6E
Date: MAY 1991
Corporate Bulletin No.: 116515

Subject:
ENHANCED EGR DIAGNOSTICS

Model and Year:
1990-91 CAMARO AND CORVETTE WITH 5.0L AND 5.7L ENGINES

SERVICE UPDATE:
This bulletin serves to enhance EGR diagnostics (Code 32) in the 1990 5.7L (VIN 8) "Y" Carline and 1990-91 5.0L (VIN F) and 5.7L (VIN 8) "F" Carline Service Manuals, Section 6E3 "Driveability And Emissions."