Skip to content
Tahoe / Yukon Service Manual

DTC P26E4-P26E6

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 P26E4 Starter Drive Control Circuit DTC P26E5 Starter Drive Control Circuit Low DTC P26E6 Starter Drive Control Circuit High For symptom byte information, refer to Symptom Byte List Diagnostic Fault Information

Circuit Number Circuit Function Short to Ground Open/High Resistance Short to Voltage Signal Performan
4325 Control P26E5 P26E4 P26E6 —
450 Ground — P26E4 — —

Circuit/System Description When the ignition switch is placed in the START position, a discrete signal is supplied to the K9  Body Control Module (BCM) notifying it that the ignition is in the START position. The BCM then sends a message to the K20 Engine Control Module (ECM) that crank has been requested. The K20 Engine Control Module then verifies that the transmission is in Park/Neutral. If it is, the K20  Engine Control Module then supplies 12 V to the control circuit 4325 of the KR27C Engine Restart Relay. When this occurs, B+ battery voltage is supplied through the switch of the KR27C Engine Restart Relay circuit 4358 to engage starter pinion. If the voltage is out of range or there is an open/high resistance condition on control circuit 4325 or ground circuit 450 the fault will set the appropriate DTC during engine cranking. Conditions for Running the DTC The ignition is in the START position, engine cranking requested. The system voltage is between 9.5–18 V. Conditions for Setting the DTC The K20 Engine Control Module detects improper voltage on the control circuit 4325 of the KR27C  Engine Restart Relay. Action Taken When the DTC Sets DTC P26E4, P26E5, and P26E6 are C type DTCs. Conditions for Clearing the DTC DTC P26E4, P26E5, and P26E6 are C type DTCs. Diagnostic Aids The last 2 digits of the circuit number are significant in identifying its power and/or ground function. – Circuits ending in 42 are primary fused B+ circuits (generally the first fuse in the circuit after the battery) – Circuits ending in 40 are secondary fused circuits (generally fuses in a fuse block after the primary circuit) – Circuits ending in 39 and 41 are ignition voltage circuits. – Circuits ending in 50 are grounds. – Circuits ending in 51 are low reference (ground). Reference Information Schematic Reference Starting and Charging Schematics Connector End View Reference Master Electrical Component List Description and Operation Starting System Description and Operation 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 for scan tool information Circuit/System Testing

  1. Ignition OFF and all vehicle systems OFF, disconnect the KR27C Engine Restart Relay. It may take up to 2 min for all vehicle systems to power down.
  2. Verify a test lamp illuminates between ground circuit terminal 86 and B+. ⇒ If the test lamp does not illuminate 2.1. Repair the open/high resistance on circuit 450 or ground connection. ⇓ If the test lamp illuminates
  3. Ignition on, connect a test lamp between the control circuit terminal 85 and ground.
  4. Verify the test lamp turns ON and OFF while commanding the Starter Drive ON and OFF with the scan tool. ⇒ If the test lamp is always OFF 4.1. Test circuit 4325 for a short to ground. ⇒ If a short to ground is found, repair the fault on the circuit. ⇓ If a short to ground is not found 4.2. Test circuit 4325 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open/high resistance is not found 4.3. Replace the K20 Engine Control Module. ⇒ If the test lamp is always ON 4.1. Test circuit 4325 for a short to voltage. ⇒ If a short to voltage is found, repair the fault on the circuit. ⇓ If a short to voltage is not found 4.2. Replace the K20 Engine Control Module. ⇓ If the test lamp turns ON and OFF
  5. Test or replace the KR27C Engine Restart Relay. Component Testing Relay Test
  6. Ignition OFF, disconnect the appropriate relay.
  7. Test for 70–150 Ω between terminals (85 or 1) and (86 or 2). ⇒ If less than 70 or greater than 150 Ω Replace the relay. ⇓ If between 70–150 Ω
  8. Test for infinite resistance between the terminals listed below: (30 or 3) and (86 or 2) (30 or 3) and (87 or 5) (30 or 3) and (85 or 1) (85 or 1) and (87 or 5) (86 or 2) and (87 or 5) ⇒ If less than infinite resistance Replace the relay. ⇓ If infinite resistance
  9. Install a 3 A fused jumper wire between relay terminal (85 or 1) and 12 V. Install a jumper wire between relay terminal (86 or 2) and ground.
  10. Test for less than 5.0 Ω between terminals (30 or 3) and (87 or 5). ⇒ If 5.0 Ω or greater Replace the relay. ⇓ If less than 5.0 Ω
  11. A fault is not currently present and may be an intermittent condition. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Electrical Relay Replacement Starter Replacement Control Module References for control module replacement, programming, and setup.