C4 Diagnostic Trouble Codes

Codes, Codes, Codes… Have you noticed “SYS” intermittently showing up in your 1990-1996 Corvette’s speedometer display?  This means there is a trouble code stored in one of the on-board control modules.  When the 1990 Corvette debuted, GM introduced ECM (Engine Control Module) and CCM (Central Control Module) trouble codes.   In addition, ABS/ASR (Anti-lock Brake System/Acceleration […]

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C4 Fuel Injection Overview

Speed density was the first fuel control system used on 1982-1984 Corvettes. It was also used on the 1990-1993 cars. Speed density uses a manifold absolute pressure sensor (MAP sensor) to calculate the necessary fuel load. The 1990-1991 cars have a MAP sensor bolted directly to the intake plenum. The 1992-1993 cars have the MAP […]

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