Code
P1686
HUMMER
P — Powertrain
Driver 5 Line 6
AI status
Completed
Completed
100%
Causes
- Open circuit in the Driver 5 / Line 6 harness
- Short to ground on the Driver 5 / Line 6 wire
- Short to battery/ignition voltage on the Driver 5 / Line 6 wire
- Faulty or intermittent load (motor, solenoid, valve, relay) on that circuit
- Corroded/loose connector or terminal at the load or module
- Faulty PCM/BCM/ECM driver transistor or internal electronics
Symptoms
- Malfunction indicator lamp (MIL) or dash warning lamp illuminated
- The specific component controlled by Driver 5 (line 6) inoperative or intermittent (e.g., pump, solenoid, heater, relay)
- Blown fuses or repeated fuse failures on related circuit
- Unusual battery drain or inability to activate the circuit
- Possible loss of related system functionality (depends on the exact load)
What to check
- Read freeze frame and live data from the controller to confirm conditions when the fault set
- Identify which physical component corresponds to Driver 5 / Line 6 from vehicle wiring diagram/service manual
- Visually inspect wiring harness, connectors, and terminals for damage, corrosion, pin push-out, or water intrusion
- Check fuses, fusible links and relays associated with the circuit
- Backprobe the driver pin at the module and the load connector while operating the circuit (use proper safety and manufacturer procedures)
- Measure resistance of the load to ground and to battery (with power disconnected) to detect short or open
Signal parameters
- Inactive (off) driver voltage: ~0–0.5 V (pulled to ground) or as specified by manufacturer
- Active (on) driver voltage: near battery voltage (~11–14 V) or PWM switching between ground and battery depending on design
- Expected current draw: varies by load — compare measured current to factory specification (excessive current indicates short/failed load)
- If PWM: switching frequency and duty cycle per service manual (verify waveform with scope)
Diagnostic algorithm
- Retrieve freeze frame, live data and complete DTC list; record operating conditions when fault set.
- Consult vehicle wiring diagram to locate Driver 5 / Line 6 pin, connector, associated fuse/relay and controlled component.
- Visually inspect connectors, pins and wiring for corrosion, damage or water entry. Repair any obvious damage and clear the code to retest.
- With ignition off, disconnect the load. Measure resistance between the driver output and ground and between output and battery to check for short or open.
- With backprobe or harness pin access, measure output voltage at the module with the load connected while commanding the circuit on/off. Compare to expected voltages.
- If output is shorted to ground or battery, isolate section of harness to locate short (disconnect connectors sequentially) and repair wiring.
- If the load shows abnormal resistance or draws excessive current when powered, replace or bench-test the load (motor/solenoid/relay).
- If wiring and load check good and the module output still behaves incorrectly (stuck high/low or no switching), suspect module driver failure and verify with scope or substitute known-good module if available.
- After repair, clear codes, perform functional test and confirm code does not return under the same operating conditions.
Likely causes
- Wiring chafed and contacting chassis ground (short to ground)
- Connector pins corroded or pushed out causing open/ intermittent connection
- Load (actuator/valve/relay) failed and drawing excessive current or shorted
- Module driver transistor damaged by previous overcurrent event
- Protective fuse/relay failed or intermittent
Fault status
Status
Controller detected a fault on Driver 5 (Line 6) output circuit — open, short, excessive current, or internal driver malfunction.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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Repair manuals
Manual library for HUMMER
138
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