B2701

Code

HUMMER B — Body

Ignition Shift Interlock Circuit Range/Performance

Brand: HUMMER

Type: B — Body

Views: UK: 12 EN: 16 RU: 12

AI status

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Page language: EN

Causes

Open or short in shift interlock wiring or connector
Failed shift lock solenoid/actuator
Faulty ignition switch or key cylinder sensor
Park/neutral position (range) sensor or gear selector switch fault
Poor ground or low battery/voltage supply to the interlock circuit
Corroded or damaged connector pins at the interlock/shift assembly

Symptoms

Unable to shift out of Park or intermittent ability to shift
Key may be trapped in ignition or will not release
Dash message or lamp related to shift interlock or transmission range
Unexpected shifting behavior or transmission may be locked in Park
Clicking noise from shift interlock area when attempting to shift or remove key

What to check

Retrieve freeze frame and all related DTCs with a scan tool; record data and attempt to reproduce condition
Visually inspect interlock solenoid, shift assembly, connectors and wiring for damage, corrosion, or pin push-out
Check fuses and relays related to ignition, BCM and shift interlock circuits
Verify battery voltage is healthy (recommended >12.4 V) and charging system is functioning
Backprobe interlock solenoid connector while operating key/shift to observe voltage/pulse behavior with a scan tool or DVOM
Check continuity and resistance of interlock solenoid coil and compare to specification

Signal parameters

Supply voltage to interlock circuit: typically battery voltage present with key ON (~9–14 V)
Control signal to solenoid: switched 0 V/near battery voltage or PWM depending on vehicle design — should change when key/shift conditions change
Solenoid coil resistance: expected low resistance (typical range ~10–40 Ω for many actuators) — check OEM spec
Park/neutral switch: digital or switched signal that changes state when selector is in Park; should consistently toggle between defined logic levels or voltages when lever moved

Diagnostic algorithm

Connect a capable scan tool; read and record B2701 and any related codes. Clear codes and attempt to reproduce. Note any accompanying modules reporting communication faults.
Verify battery voltage and inspect fuses/relays for ignition, BCM/IP and transmission interlock circuits. Replace if blown and retest.
Visually inspect harnesses and connectors at the shifter, solenoid and steering column for corrosion, damage, or loose pins. Repair as required.
Backprobe the interlock solenoid connector. With key ON and when attempting to shift, observe whether proper supply and control signals are present. If no supply, trace to fuse/ignition feed.
Measure solenoid coil resistance with the connector disconnected. If open or shorted outside spec, replace the solenoid.
Verify Park/Neutral (range) switch/gear selector sensor outputs with the scan tool or DVOM while moving the shifter through all positions. Replace or adjust sensor if signals are incorrect or intermittent.
Command the interlock solenoid (if supported) via the scan tool and confirm operation. If the module does not command but inputs are correct, suspect BCM/IPC or module programming fault.
Check for mechanical binding by manually actuating the interlock (service release) and verifying shift movement. Free or repair any mechanical obstructions.
After repairs, clear codes and perform full functional verification including several key-on/shift cycles. If faults persist and wiring and components test good, consider module replacement or reprogramming per OEM procedures.

Likely causes

Interlock solenoid coil open or shorted
Loose/chafed harness between solenoid and BCM or ignition switch
Faulty park/neutral position switch reporting incorrect range
Blown fuse or poor constant/ignition-switched power to circuit
Connector corrosion at shifter assembly or steering column

Fault status

⚠️ Status

Ignition shift interlock circuit is out of expected range or not performing. The control module detected inconsistent or missing signals from the shift interlock/park-range circuit and set DTC B2701.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.5 hours

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