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Tahoe / Yukon Service Manual

DTC P0116, P149A, or P149D

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5898983 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P0116 Engine Coolant Temperature Sensor Performance DTC P149A Engine Coolant Temperature Sensor 2 Not Plausible DTC P149D Engine Coolant Temperature Sensor 5 Not Plausible Typical Scan Tool Data Engine Coolant Temperature Sensor & Engine Coolant Temperature Sensor 2-6

Circuit Short to Ground Open Short to Voltage
Operating Conditions: Engine = Idling — At normal operating temperature. Parameter Normal Range: 88 to 105°C (190 to 221°F)
Signal 150°C (302°F) −40°C (−40°F) −40°C (−40°F)
Low Reference — −40°C (−40°F) —

Circuit/System Description For an overview of the component/system, refer to: Cooling System Description and Operation

Circuit Description
Signal The control module input circuit has an internal resistance connected to 5 V.
Low Reference Grounded through the control module.

Component Description The sensor is a negative temperature coefficient thermistor. As the temperature of the air, fluid, or metal increases, the resistance of the sensor decreases, varying the voltage on the signal circuit. B34 Engine Coolant Temperature Sensor

Component Description
K20 Engine Control Module The control module contains a microprocessor used to process input data to control outputs. The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly.

Conditions for Running the DTC DTCs related to the following system/component = Not Set B9 Ambient Air Temperature Sensor B34 Engine Coolant Temperature Sensor — Circuit B36 Engine Oil Temperature Sensor B65 Manifold Absolute Pressure and Intake Air Temperature Sensor B203 Radiator Coolant Temperature Sensor Ambient Air Temperature = Warmer than −20°C (−4°F) Engine Block Heater = Inactive /Not Detected Engine Off Time = For greater than 6 h Ignition = On Frequency the DTC runs = Once — Per cold start-up — After the running conditions are met Conditions for Setting the DTC Engine Coolant Temperature Sensor or Engine Coolant Temperature Sensor 2-6 & Intake Air Temperature Sensor = Not within 7.40°C (13.32°F) of each other @ Cold Start-Up Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type B DTC Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type B DTC Diagnostic Aids After starting a cold engine, the following scan tool parameter value should rise steadily and then stabilize: Engine Coolant Temperature Sensor / Intake Air Temperature Sensor Engine Coolant Temperature Sensor — Description / Production Location

Component Location
B34A Engine Coolant Temperature Sensor 1 Engine Coolant Inlet Pipe
B34B Engine Coolant Temperature Sensor 2 Engine Block — Front
B34E Engine Coolant Temperature Sensor 5 Engine Block — Rear

Reference Information Schematic Reference Engine Controls Schematics Engine Heating/Cooling Schematics Connector End View Reference Master Electrical Component List Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs DTC Type Reference Powertrain Diagnostic Trouble Code (DTC) Type Definitions Scan Tool Reference Control Module References Circuit/System Verification

  1. Verify no other DTCs are set. ⇒ If other DTCs are set Refer to: Diagnostic Trouble Code (DTC) List - Vehicle ⇓ If no other DTCs are set
  2. Ignition/Vehicle » Off — For greater than 6 h
  3. Ignition » On / Vehicle » In Service Mode
  4. Verify the following parameters are within 15.8°C (28°F) of each other: Ambient Air Temperature Sensor ECT Sensor IAT Sensor ⇒ If not within 15.8°C (28°F) of each other { Ambient Air Temperature Sensor } Refer to: DTC P0071-P0074 { ECT Sensor } Refer to: Circuit/System Testing { IAT Sensor } Refer to: DTC P0097-P0099, P00F4-P00F6, or P0112-P0114 ⇓ If within 15.8°C (28°F) of each other
  5. Verify the scan tool parameter: ECT Sensor = The value should not spike or drop out. Perform the action while monitoring the parameter: Wiggle the harness and connector: B34 Engine Coolant Temperature Sensor Wiggle the harness and connector: K20 Engine Control Module ⇒ If the value spikes or drops out Repair as necessary » Wiring / Terminal(s) / Electrical Connector(s) ⇓ If the value does not spike or drop out
  6. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. Verify the DTC does not set. ⇒ If the DTC sets Refer to: Circuit/System Testing ⇓ If the DTC is not set
  7. All OK. Circuit/System Testing
  1. Ignition/Vehicle & All vehicle systems » Off
  2. Disconnect the appropriate electrical connector: B34 Engine Coolant Temperature Sensor
  3. Test for less than 10 Ω between the test points: Low Reference circuit terminal 2 & Ground ⇒ If 10 Ω or greater 3.1. Disconnect the appropriate electrical connector: K20 Engine Control Module 3.2. Test for less than 2 Ω between the test points: Low Reference circuit terminal 2 @ Component harness & The other end of the circuit @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If less than 10 Ω
  4. Ignition » On / Vehicle » In Service Mode
  5. Verify the scan tool parameter: ECT Sensor = Colder than −39°C (−38°F) ⇒ If warmer than −39°C (−38°F) 5.1. Ignition/Vehicle » Off 5.2. Disconnect the appropriate electrical connector: K20 Engine Control Module 5.3. Test for infinite resistance between the test points: Signal circuit terminal 1 @ Component harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇒ If infinite resistance » Replace the component: K20 Engine Control Module ⇓ If colder than −39°C (−38°F)
  6. Connect a 3 A fused jumper wire between the test points: Signal circuit terminal 1 & Low Reference circuit terminal 2
  7. Verify the scan tool parameter: ECT Sensor = Warmer than 149°C (300°F) ⇒ If 149°C (300°F) or colder 7.1. Ignition/Vehicle » Off & Remove » Jumper wire(s) 7.2. Disconnect the appropriate electrical connector: K20 Engine Control Module 7.3. Ignition » On / Vehicle » In Service Mode 7.4. Test for less than 1 V between the test points: Signal circuit terminal 1 @ Component harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇓ If less than 1 V 7.5. Ignition/Vehicle » Off 7.6. Test for less than 2 Ω between the test points: Signal circuit terminal 1 @ Component harness & The other end of the circuit @ Control module harness ⇒ If 2 Ω or greater » Repair the open/high resistance in the circuit. ⇒ If less than 2 Ω » Replace the component: K20 Engine Control Module ⇓ If warmer than 149°C (300°F)
  8. Test or replace the component: B34 Engine Coolant Temperature Sensor Component Testing
  9. Ignition/Vehicle » Off
  10. Disconnect the appropriate electrical connector: B34 Engine Coolant Temperature Sensor
  11. Test the resistance between the test points: Signal circuit terminal 1 & Low Reference circuit terminal 2 @ Component
  12. Verify the value is within the range listed in the table: Temperature Versus Resistance ⇒ If not in the specified range Replace the appropriate component: B34 Engine Coolant Temperature Sensor ⇓ If in the specified range
  13. Test for infinite resistance between the test points: Each terminal of the component & The component’s housing ⇒ If less than infinite resistance Replace the appropriate component: B34 Engine Coolant Temperature Sensor ⇓ If infinite resistance
  14. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Engine Coolant Temperature Sensor Replacement - Water Pump Inlet Pipe — B34A Engine Coolant Temperature Sensor 1 — Water Pump Inlet Pipe Engine Coolant Temperature Sensor Replacement - Engine Block - Front — B34B Engine Coolant Temperature Sensor 2 — Engine Block — Front Engine Coolant Temperature Sensor Replacement - Engine Block - Rear — B34E Engine Coolant Temperature Sensor 5 — Engine Block — Rear For control module replacement, programming, and setup refer to: Control Module References