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Tahoe / Yukon Service Manual

Engine Oil Pressure Gauge Inaccurate or Inoperative (LM2)

Engine Oil Pressure Gauge Inaccurate or Inoperative (LM2) 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 Descriptors DTC P0521 Engine Oil Pressure Sensor Performance DTC P0522 Engine Oil Pressure Sensor Circuit Low Voltage. DTC P0523 Engine Oil Pressure Sensor Circuit High Voltage Diagnostic Fault Information

Circuit Short to Ground High Resistanc e Open Short to Voltage Signal Performan
Engine Oil Pressure 5 V Reference P0522 1 P0522 P0523 P0521
Engine Oil Pressure Sensor Signal P0522 1 P0522 P0523 P0521
Low Reference — 1 P0523 — P0521
1. Engine Oil Pressure Gauge Inaccurate or Inoperative

Circuit/System Description The engine oil pressure sensor changes voltage based on the engine oil pressure. The engine oil pressure sensor is a 3-wire sensor comprising of the signal circuit, the low reference circuit and the 5 V reference circuit. The engine control module (ECM) supplies 5 V to the engine oil pressure sensor via the 5 V reference circuit and provides ground via the low reference circuit. The ECM monitors the signal circuit of the engine oil pressure sensor to determine if the engine oil pressure sensor voltage is within the normal operating range of approximately 1–4 V. When the engine oil pressure is high, the engine oil pressure sensor voltage is high and the ECM senses a high signal voltage. When the engine oil pressure is low, the engine oil pressure sensor voltage is low and the ECM senses a low signal voltage. The ECM sends the engine oil pressure information to the P16 Instrument Panel Cluster Control Module via serial data. The P16 Instrument Panel Cluster Control Module will illuminate or display the engine oil pressure indicator when the engine oil pressure is low. Conditions for Running the DTC The engine is running. Conditions for Setting the DTC P0521 The ECM detects that measured oil pressure is at least 47 kPa (6.8 psi) less than or 50 kPa (7.3 psi) higher than the predicted oil pressure. The engine oil pressure is outside of a calculated working range determined by engine speed and temperature. One of the above conditions are present for greater than 4 s. P0522 The ECM detects that the engine oil pressure sensor signal circuit is less than 0.2 V. The above condition is present for greater than 10 s. P0523 The ECM detects that the engine oil pressure sensor signal circuit is greater than 4.8 V. The above condition is present for greater than 10 s. Action Taken When the DTC Sets The ECM records the operating conditions at the time the diagnostics test fails. The ECM displays this information in the Failure Records on the scan tool. The P16 Instrument Panel Cluster Control Module illuminates the engine oil pressure indicator. Conditions for Clearing the DTC The DTC becomes history when the conditions for setting the DTC are no longer present. The history DTC clears after 40 malfunction-free warm-up cycles. Diagnostic Aids DTC P0521 can set if engine oil pressure is outside the calculated engine oil pressure model stored in the engine control module. This can be an indication of improper engine oil level, poor engine oil condition, or mechanical engine issues causing lower than expected engine oil pressure. Reference Information Schematic Reference Instrument Cluster Schematics Connector End View Reference Master Electrical Component List Description and Operation Indicator/Warning Message Description and Operation Instrument Cluster Description and Operation Electrical Information Reference Circuit Testing Connector Repairs Testing for Intermittent Conditions and Poor Connections Wiring Repairs Scan Tool Reference Control Module References for scan tool information Circuit/System Verification

  1. Verify correct engine oil level and condition.
  2. Ignition ON/Vehicle in Service Mode.
  3. Verify the scan tool Engine Oil Pressure parameter is 0 psi (0 kPa). ⇒ If not 0 psi (0 kPa) Refer to Circuit/System Testing. ⇓ If 0 psi (0 kPa)
  4. Engine running.
  5. Verify actual engine oil pressure is within specified range. Refer to Oil Pressure Diagnosis and Testing in Displays and Gauges Component Replacement Reference.
  6. Verify the scan tool Engine Oil Pressure parameter is within specified range. ⇒ If not within specified range Refer to Circuit/System Testing. ⇓ If within specified range
  7. Verify the engine oil pressure displayed on the P16 Instrument Panel Cluster Control Module is within specified range. ⇒ If not within specified range Test or replace the P16 Instrument Panel Cluster Control Module. ⇓ If within specified range
  8. All OK. Circuit/System Testing
  1. Ignition OFF/Vehicle OFF and all vehicle systems OFF, disconnect the harness connector at the B37B Engine Oil Pressure Sensor. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 15 Ω between the low reference circuit terminal 2 and ground. ⇒ If 15 Ω or greater 2.1. Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module. 2.2. Test for less than 2 Ω in the low reference circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, replace the K20 Engine Control Module. ⇓ If less than 15 Ω
  3. Ignition ON/Vehicle in Service Mode.
  4. Test for 4.8–5.2 V between the 5 V reference circuit terminal 3 and ground. ⇒ If less than 4.8 V 4.1. Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module. 4.2. Test for infinite resistance between the 5 V reference circuit and ground. ⇒ If less than infinite resistance, repair the short to ground on the circuit. ⇓ If infinite resistance 4.3. Test for less than 2 Ω in the 5 V reference circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, replace the K20 Engine Control Module. ⇒ If greater than 5.2 V 4.1. Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON. 4.2. Test for less than 1 V between the 5 V reference circuit and ground. ⇒ If 1 V or greater, repair the short to voltage on the circuit. ⇒ If less than 1 V, replace the K20 Engine Control Module. ⇓ If between 4.8–5.2 V
  5. Verify the scan tool Engine Oil Pressure parameter is less than 14 kPa (2 psi). ⇒ If 14 kPa (2 psi) or above 5.1. Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON. 5.2. Test for less than 1 V between the signal circuit terminal 1 and ground. ⇒ If 1 V or greater, repair the short to voltage on the circuit. ⇒ If less than 1 V, replace the K20 Engine Control Module. ⇓ If below 14 kPa (2 psi)
  6. Install a 3 A fused jumper wire between the signal circuit terminal 1 and the 5 V reference circuit terminal 3.
  7. Engine running.
  8. Verify the scan tool Engine Oil Pressure parameter is greater than 800kPa (116psi). ⇒ If 800kPa (116psi) or less 8.1. Ignition OFF/Vehicle OFF, disconnect the harness connector at the K20 Engine Control Module. 8.2. Test for infinite resistance between the signal circuit terminal 1 and ground. ⇒ If less than infinite resistance, repair the short to ground on the circuit. ⇓ If infinite resistance 8.3. Test for less than 2 Ω in the signal circuit end to end. ⇒ If 2 Ω or greater, repair the open/high resistance in the circuit. ⇒ If less than 2 Ω, replace the K20 Engine Control Module. ⇓ If greater than 800kPa (116psi)
  9. Test or replace the B37B Engine Oil Pressure Sensor. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Displays and Gauges Component Replacement Reference Control Module References for control module replacement, programming and setup