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Tahoe / Yukon Service Manual

DTC P0622

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 P0622 Generator F-Terminal Circuit 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
2 B+ P0621 P0621 — —
25 Control P0621 P0621 P0621 —
23 Signal P0622 P0622 P0622 P0622

Circuit/System Description The G13 Generator provides a PWM feedback signal of the voltage output through the signal circuit 23, also known as the F-terminal, to the K20 Engine Control Module. This information is sent to the K9 Body Control Module. The signal circuit 23 is a PWM signal of 60–460 Hz with a duty cycle of 0–100%. Normal duty cycle is between 5–95%. 0–5% and 95–100% are for diagnostic purposes. 0–5% indicates an open or short to ground and 95–100% indicates a short to voltage. Conditions for Running the DTC Ignition ON, engine OFF (Prior to Ignition ON, the ignition must have been OFF for at least 5 s) Engine running at less than 3,000 RPM DTC P0622 is not set Conditions for Setting the DTC Ignition ON, engine OFF: The K20 Engine Control Module detects a PWM signal on circuit 23 that is greater than 65% for 5 s Engine running at less than 3,000 RPM: The K20 Engine Control Module detects a PWM signal on circuit 23 that is less than 5% for 30 s Action Taken When the DTC Sets 6.2 L (L87) Engine DTC P0622 is a type A DTC Except 6.2 L (L87) Engine DTC P0622 is a type C DTC Conditions for Clearing the DTC 6.2 L (L87) Engine DTC P0622 is a type A DTC Except 6.2 L (L87) Engine DTC P0622 is a type C DTC Diagnostic Aids Circuit numbers are significant in identifying its power or ground function. Single digit circuit numbers are identified different than the multiple digit circuits. The multiple digit circuit number functions are identified by the last 2 digits of the circuit number – Circuit 1 is Primary Battery positive voltage. – Circuit 2 is Battery positive voltage. – Circuit 3 is Run/Crank ignition voltage. – Circuit 4 is Accessory voltage. – Circuit 5 is Crank voltage. – 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) circuits. Reference Information Schematic Reference Starting and Charging Schematics Connector End View Reference Master Electrical Component List Description and Operation Charging 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 Verification

  1. Engine running.
  2. Verify the scan tool Generator F-Terminal Signal parameter is between 5–90%. ⇒ If not between 5–90% Refer to Circuit/System Testing. ⇓ If between 5–90%
  3. Verify the scan tool Generator F-Terminal Signal parameter changes when turning the headlamps ON and OFF. ⇒ If the parameter does not change Refer to Circuit/System Testing. ⇓ If the parameter changes
  4. 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.
  5. Verify DTC P0622 is not set as current. ⇒ If DTC P0622 is set as current Refer to Circuit/System Testing. ⇓ If DTC P0622 is not set as current or is set as history
  6. A fault is currently not present and may be an intermittent condition. Circuit/System Testing
  7. Verify a test lamp illuminates between the G13 Generator B+ circuit terminal A X2 and ground. ⇒ If the test lamp does not illuminate and the circuit fuse is good 1.1. Test circuit 2 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 1.2. Verify the fuse is not open and there is voltage at the fuse. ⇒ If the test lamp does not illuminate and the circuit fuse is open 1.1. Test circuit 2 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. 1.2. Replace the G13 Generator. ⇓ If the test lamp illuminates
  8. Ignition Off, disconnect the X1 connector at the G13 Generator, engine running.
  9. Verify the scan tool Generator F-Terminal Signal parameter is less than 5%. ⇒ If 5% or greater 3.1. Test circuit 23 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 3.2. Replace the K20 Engine Control Module. ⇓ If less than 5%
  10. Install a 3 A fused jumper wire between signal circuit terminal 2 and B+, engine running.
  11. Verify the scan tool Generator F-Terminal Signal parameter is greater than 95%. ⇒ If 95% or less 5.1. Test circuit 23 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 5.2. Test circuit 23 for an open/high resistance. ⇒ If an open/high resistance is found, repair the fault on the circuit. ⇓ If an open or high resistance is not found 5.3. Replace the K20 Engine Control Module. ⇓ If greater than 95%
  12. Replace the G13 Generator. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair. Generator Replacement Control Module References for control module replacement, programming, and setup