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1994 - 1996 Corvette: Diagnostic Trouble Codes

DTC #11:  Malfunction Indicator Lamp Circuit.
DTC #13:  Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14:  Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15:  Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16:  Distributor Ignition System Low Pulse.
DTC #18:  Injector Circuit.
DTC #21:  Throttle Position Sensor Circuit Voltage High.
DTC #22:  Throttle Position Sensor Circuit Voltage Low.
DTC #23:  Intake Temperature Sensor Circuit Voltage High.
DTC #24:  Vehicle Speed Sensor Circuit.
DTC #25:  Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26:  Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27:  EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28:  Transmission Range Pressure Switch Assembly Fault.
DTC #29:  Secondary Air Injection Pump Circuit.
DTC #32:  Exhaust Gas Recalculation.
DTC #33:  Manifold Absolute Pressure Sensor Circuit High.
DTC #34:  Manifold Absolute Pressure Sensor Circuit Low.
DTC #36:  Distributor Ignition System High Pulse.
DTC #37:  Brake Switch Stuck On.
DTC #38:  Brake Switch Stuck Off.
DTC #41:  Ignition Control Circuit Open.
DTC #42:  Ignition Control Circuit Shorted.
DTC #43:  Knock Sensor Circuit.
DTC #44:  Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45:  Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47:  Knock Sensor Circuit Or Module Missing.
DTC #48:  Mass Air Flow Sensor Circuit.
DTC #50:  System Voltage Low.
DTC #51:  EPROM Programming Error.
DTC #52:  Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53:  System Voltage Low.
DTC #55:  Fuel Lean Monitor.
DTC #58:  Transmission Fluid Temperature Sensor Circuit Low.
DTC #59:  Transmission Fluid Temperature Sensor Circuit High.
DTC #62:  Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63:  Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64:  Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65:  Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66:  A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67:  A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68:  A/C Relay Circuit.
DTC #69:  A /C Clutch Circuit.
DTC #70:  A/C Clutch Relay Driver Circuit.
DTC #72:  Vehicle Speed Sensor Loss.
DTC #73:  Pressure Control Solenoid Circuit Current Error.
DTC #74:  Traction Control System Circuit Low.
DTC #75:  Transmission System Voltage Low
DTC #77:  Primary Cooling Fan Relay Control Circuit.
DTC #78:  Secondary Cooling Fan Relay Control Circuit.
DTC #79:  Transmission Fluid Overtemp.
DTC #80:  Transmission Component Slipping.
DTC #81:  Transmission 2-3 Shift Solenoid Circuit.
DTC #82:  Transmission 1-2 Shift Solenoid Circuit.
DTC #83:  Torque Converter Solenoid Voltage High.
DTC #84:  3-2 Control Solenoid Circuit.(Auto Only).
DTC #84:  2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85:  Transmission TCC Stock On.
DTC #90:  Transmission TCC Solenoid Circuit.
DTC #91:  One To Four Upshift Lamp(Manual Only).
DTC #97:  VSS Output Circuit.
DTC #98:  Tachometer Output Signal Voltage Wrong.

  1. I have been researching possible Opti-Spark issues as to my 95 Vette after replacing it after it developed a miss that got worse day by day. It started on the first crank, idle was smooth as I reinstalled coolant. Did minor test drive around the block with no issues. Too tired after the meticulous install and would test drive next day. Started fine, idle fine but after only 3+ miles started to miss badly and eventually quit. Would not immediately start again. Let sit for about an hour, started ok and managed to get back home. Would start ok again but had the miss. Made appointment with a local GMC dealer to do Diagnostic Test as now the car will not start? They said the replaced Opti-Spark was bad??? I have had my doubts about their analysis as I felt I had purchased a quality part from a reputable Corvette company, but the part was not made in USA. What I have found is the Opti-Spark is no longer made by GM and the after-market parts are total failures most of the time. How can this be? So, I have been researching Codes, relays, coils and wiring that might be the problem!!! Most all of my searches have resulted in "failed Opti-Sparks", some 2 & 3 times after being installed for limited miles! The LT1 5.7 is a great motor but GM married it to a "drunken Opti family" and that is the best I can describe one of the worst parts and its location on an engine. Who in their right mind designs an electrical part to be installed below a water part with a "coolant weep hole"? Most of the reported failures seem to be due to the two small screws that hold the Rotor Button in place coming loose or/and those with bad worn-out oil seals! Those having moderate success, even with the most expensive ones, are removing the outer protective cover and "Loc-Tite" the screws. Sad you have to do this with a new $600+ part. So, my final path has led me to Petris Engineering in Alabama with an above average success rate due to their in-house manufacturing in USA. They secure those two Rotor screws with Loc-Tite on assemble and use the top-rated Mitsubishi Optical sensor just like the original GM unit. This is a very difficult tear down & reinstall that I am not looking forward to doing again!!!

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