AgentEran

I pulled my codes last night after observing the SES light illuminate after a long drive.. I got the following codes:

Module 1 - H72 & H74

Module 4 - H28 & H32

Ive searched around and found conflicting definitions for these codes..

Based on this;

http://tech.corvettecentral.com/2011...trouble-codes/

My codes are as follows:

DTC 72 – Vehicle Speed Sensor Loss
DTC 74 – Traction Control System (TCS) Circuit Low

DTC 32 – Exhaust Gas Recirculation (EGR)
DTC 28 – Transmission Range (TA) Pressure Switch Assembly Fault

Is this accurate?

& if so, I am a little confused because the car is a M6, 1993 LT1. It seems like Vehicle Speed Sensor and Transmission Range (TA) Pressure Switch Assembly are components of automatic transmission cars?

74 & 32 seem straight forward, but I am a little confused with 72 & 28.

Anyone have any experience with these codes, or be able to tell me if I am correct in my interpretation of my codes?

92ragtop

Assuming that the 1993 is the same as the 1992, the code descriptions from my 1992 FSM are:

28 ECM detected the wrong potential voltage at the #3 quad-driver module circuit for 3 seconds.
32 EGR open command did not change the fuel mixture when the command was given during off idle operation. EGR opening should cause the mixture to be slightly richer because of the low oxygen content of the exhaust gas.
72 2nd or 3rd gear switch was open for 1.5 seconds when vehicle speed was above 30 MPH with engine speed greater than 5000 RPM and a throttle angle (TPS) above 70%.
74 EBCM operating voltage falls below 9.0

AgentEran

Thanks for the data.. that is definitely different from the info I found online.

Now on to figuring out what the hell is needed to address 28, 72 and 74..

fpnmf

Here's a great place to start!!

http://www.ebay.com/itm/1993-CHEVROLET-CORVETTE-SHOP-SERVICE-MANUAL-set-2-UsedLowPrice-/251929897812?hash=item3aa8312b54&vxp=mtr

WVZR-1

The codes you pulled are all HISTORY codes or so you mentioned. I'd clear all of the codes and do it again using an appropriate scanner for detection of CURRENT DTC's. What drivability issue are you having?

The 72 and 74 in earlier cars was common CCM error when an after-market radio had been added. Is your radio OE? I'm betting NOT. Those codes are discussed in the link you provided. I believe the 28 is usually an AC Clutch issue or cooling fan.

AgentEran

I dont really have any drive ability issues, besides a slight hesitation when going from idle to say half throttle..

Im going to replace my radiator because its leaking, but while i am in there I am going to do the water pump. When Im doing that im going to replace the spark plug wires and spark plugs as well.

After some thought, Im beginning to think that 28 & 32 are related. And that the EGR not operating well can cause some issues in the lower RPM range.

AgentEran

And indeed, there is an aftermarket radio installed..

Cliff Harris

I have found that this source for code explanations is most accurate and does a better job of breaking down the codes by year:

http://forums.corvetteforum.com/1576116036-post35.html