Low Coolant Indicator Does Not Light With Low Coolant Level (Diesel)

WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 1997 GMC Savana Special, 1997 GMC Savana Camper Special, 1997 GMC Savana, 1997 Chevrolet RV Cutaway, and 1997 Chevrolet Cutaway. However, it is still accessible from the selected car via links, so may be relevant.

Disconnect coolant level indicator module harness connector. Turn ignition switch to RUN position. Connect a non-powered test light between ground and coolant level module harness connector Pink wire terminal. If test light lights, go to next step. If test light does not light, repair open in Pink wire.
Connect a self-powered test light between ground and coolant level module harness connector Black wire terminal. If test light lights, go to next step. If test light does not light, repair open in Black wire.
Connect a fused jumper wire between ground and coolant level module harness connector Yellow/Black wire terminal. If low coolant level indicator lights, go to step 5). If low coolant indicator does not light, go to next step.
Disconnect instrument cluster harness connector. Connect a self-powered test light between instrument cluster harness connector A5 (Yellow/Black wire) and coolant level module harness connector Yellow/Black wire. If test light lights, replace instrument cluster. See INSTRUMENT CLUSTER under REMOVAL & INSTALLATION. If test light does not light, repair open in Yellow/Black wire.
Check that radiator coolant level is correct. Using an ohmmeter, measure resistance between level module harness connector Light Green wire terminal and ground. If resistance is less than 5000 ohms, go to next step. If resistance is between 10,000 and 50,000 ohms, replace coolant level sensor module.
Connect a self-powered test light between ground and coolant level module harness connector Light Green wire terminal. If test light does not light, replace coolant level sensor. If test light lights, repair short to ground in Light Green wire.