1990 chevrolet K1500 truck, 5.7 eng. THE RED LIGHT IS FLASHING ON THE DASH AND READS A CODE 4 WHAT DOES IT MEAN.
Light Flashing On dash on 1990 Chevrolet 1500 Pickup
The red light flashing is probably the "brake" light on your 1990 Chevrolet 1500 Pickup. The code 4 would indicate a fault with the RWAL valve switch. The ABS control module is seeing the RWAL valve switch closed or grounded when it should not be. Sorry I do not have a diagnostic chart available for the RWAL valve switch.