Code
P0705
HUMMER
P — Powertrain
Trans Range Switch Circuit
AI status
Completed
Completed
100%
Causes
- Damaged, corroded, or disconnected connector at the range switch or TCM/ECM
- Wiring short to power, ground, or other circuits; open or high-resistance wiring
- Faulty transmission range (selector) switch or internal switch contacts
- Misadjusted or binding shift linkage/selector mechanism
- Faulty TCM/ECM or poor input circuit on the control module
- Blown fuse or poor power/ground to the range switch circuit
Symptoms
- MIL/Check Engine lamp illuminated
- Vehicle may not start because PCM/TCM does not detect Park or Neutral
- Starter does not crank in Park/Neutral or only cranks in one position
- Incorrect or erratic gear indication on dash
- Transmission may go into limp/ failsafe mode or refuse to shift correctly
- Inability to select gears or unexpected gear changes
What to check
- Check for related codes (P0700, P0706–P0708, P0720) and freeze frame data
- Visual inspection of range switch connector, wiring harness, and grounds
- Verify power and ground to the range switch with key ON
- Backprobe range switch signal pin and monitor voltage while moving shifter through positions
- Check continuity and resistance of switch contacts per gear positions
- Inspect shift linkage/selector for proper adjustment and free movement
Signal parameters
- Range switch uses a PCM/TCM 5 V reference and returns a unique 0–5 V signal or discrete contact closures for each selector position
- Expected behavior: a distinct voltage or continuity pattern for Park, Reverse, Neutral, Drive (consult vehicle service manual for exact values)
- Typical returns: low resistance (near 0 Ω) or continuity to the terminal assigned to the current gear; open/high resistance to other gear terminals
- Intermittent spikes, floating voltages, or no return signal indicate wiring/switch issues
- If available, compare live PID values for selector position to known-good values in service data
Diagnostic algorithm
- Safety: Park vehicle, set parking brake, use wheel chocks, and follow workshop safety procedures.
- Read codes and freeze frame with a scan tool. Note any additional transmission or sensor codes.
- Visually inspect the range switch connector, wiring harness, and transmission/shifter area for damage, corrosion, loose pins, or fluid intrusion.
- Verify fuse(s) and power/ground supplies to the range switch. With key ON, check for the 5 V reference (or battery voltage where applicable) and good ground at the switch connector.
- Backprobe the signal wire(s) at the range switch; with an assistant move the selector through all positions while observing the scan tool PID or a digital multimeter. Confirm the signal changes to unique values or continuity as each gear is selected.
- Check continuity/resistance between the range switch terminals and the harness/TCM connector. Look for opens, shorts to ground or power, and high resistance. Repair wiring as necessary.
- If wiring and connections are good, bench-test or replace the range/selector switch per service manual procedures, or test the shifter assembly if externally mounted.
- If switch replacement does not clear the issue, test the TCM/ECM input circuit for shorts or replace the module only after confirming wiring and sensor operation.
- Clear codes, perform a controlled road test and verify the selector position PID and that no P0705 returns. Re-scan for codes after test.
Likely causes
- Loose, corroded or damaged connector at range switch (most common)
- Broken or chafed wire in harness between switch and TCM/ECM
- Failed range/selector switch inside transmission or on shifter assembly
- Shift linkage out of adjustment preventing correct switch contact
- Intermittent TCM/ECM input fault (less common)
Fault status
Status
P0705 — Transmission Range (TR) Switch Circuit: invalid, missing, or inconsistent selector position signal detected by the control module.
Repair difficulty: Medium
Diagnostic time: 0.5-2 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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