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P0480 1. Ignition OFF, disconnect the cooling fan low relay from the underhood fuse block. 2. Ignition ON, verify that a test lamp illuminates between the fan low relay coil voltage supply circuit and ground. If the test lamp does not illuminate, test the fan low relay coil voltage supply circuit 3. Connect a test lamp between the fan low relay coil supply voltage circuit and the fan low relay coil control circuit. With a scan tool, command the fan relay 1 ON and OFF. Verify If the test lamp remains illuminated with each command, test the relay coil control If the test lamp does not illuminate, test the relay coil control circuit for and open or a 4. If the circuits test normal, replace the fan low relay. P0481 1. Ignition OFF, disconnect the cooling fan high relay from the underhood fuse block. 2. Ignition ON, verify that a test lamp illuminates between the fan high relay coil voltage supply circuit and ground. If the test lamp does not illuminate, test the fan high relay coil voltage supply circuit 3. Connect a test lamp between the fan high relay coil supply voltage circuit and the fan high relay coil control circuit. With a scan tool, command the fan relays 2 and 3 ON and OFF. If the test lamp remains illuminated with each command, remove the fan control relay If the test lamp does not illuminate, test the fan high relay coil control circuit for and 4. If all circuits test normal, replace the fan high relay. Repair Procedures Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
2008 Chevrolet Silverado 1500 2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Relay Replacement (Attached to Wire Harness) or Relay Replacement (Within an Underhood Electrical Center or Junction Block Replacement Control Module References for ECM replacement, setup, and programming DTC P1258 Diagnostic Instructions Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Review Strategy Based Diagnosis for an overview of the diagnostic approach. Diagnostic Procedure Instructions provides an overview of each diagnostic category. DTC Descriptor DTC P1258 Engine Coolant Over temperature - Protection Mode Active Circuit/System Description The engine control module (ECM) uses the engine coolant temperature (ECT) sensor to monitor Conditions for Running the DTC The engine is running. DTC P0117 or P0118 are not set. Conditions for Setting the DTC Coolant temperature more than 132°C (270°F) for greater than 10 seconds. Action Taken When the DTC Sets DTC P1258 is a Type A DTC. The engine will operate in the Overheated Engine Protection Operating Mode. The engine coolant temperature indicator lamp, if equipped, will illuminate.
2008 Chevrolet Silverado 1500 2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
The driver information center (DIC), if equipped, may display a message. Conditions for Clearing the DTC DTC P1258 is a Type A DTC. Reference Information Description and Operation Cooling System Description and Operation Instrument Cluster Description and Operation Indicator/Warning Message Description and Operation Audible Warnings Description and Operation DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References for scan tool information Circuit/System Verification 1. Observe the engine coolant level. The engine coolant level should be within operating range. Refer to Capacities - Approximate Fluid, and Engine Coolant in the Owner's Manual. 2. Ensure that the vehicle has the correct engine coolant, with correct concentration, and is not old, contaminated or contains additives. Refer to Recommended Fluids and Lubricants in 3. Inspect the cooling system for the following: Leaks Kinked or pinched hoses, especially at the radiator Loose, missing, or damaged radiator air seals or deflectors The radiator and A/C condenser for any air flow obstructions or bent fins-Refer to IMPORTANT: If DTC P1482 is set, diagnose that DTC first.
2008 Chevrolet Silverado 1500 2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
4. Command the cooling fan speed from 0% to 100% with a scan tool. If the fan speed does not transition with the commanded states, refer to Cooling Fan Circuit/System Testing 1. Test the thermostat for correct operation. Refer to Thermostat Diagnosis. 2. Test the engine cooling system for overheating. Refer to Engine Overheating. 3. Inspect the water pump and coolant flow for correct operation. Refer to Water Pump Replacement (LU3) or Water Pump Replacement (LY6, L76 and L92) or Water 4. Inspect the engine for worn/leaking/cracked cylinder heads and engine block. Refer to Coolant in Combustion Chamber and Coolant in Engine Oil . Repair Procedures Perform the Diagnostic Repair Verification after completing the diagnostic procedure. SYMPTOMS - ENGINE COOLING Cooling System Description and Operation Cooling Fan Description and Operation (w/o LFA) Visual/Physical Inspection Inspect for aftermarket devices which could affect the operation of the Cooling System. Inspect the easily accessible or visible system components for obvious damage or conditions Intermittent Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to IMPORTANT: A small delay occurs before the ECM changes the cooling fan speed. IMPORTANT: Review the system operation in order to familiarize yourself with the system functions. Refer to the following:
2008 Chevrolet Silverado 1500 2008 ENGINE Engine Cooling - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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