Code
U1170
HUMMER
U — Network/User
Loss of Driver Door Switch Asm Serial Data
AI status
Completed
Completed
100%
Causes
- Open or short in serial data bus wiring between driver door switch assembly and BCM/other modules
- Faulty driver door switch assembly (door module)
- Faulty body control module (BCM) or gateway module
- Poor connector connections or corrosion at door harness/door jamb
- Power or ground fault to the driver door switch assembly
- Intermittent wiring damage from door movement (pinch/rolled wires)
Symptoms
- Driver door switches (lock/unlock, mirror, windows) not responding or intermittent
- Interior lighting or delay features related to door may not work
- Door-related chassis functions (keyless entry, power windows) may not operate
- DTCs related to other modules that rely on door switch data
- Possible permanent message on dash indicating module communication loss
What to check
- Connect a capable scan tool and confirm U1170 and any related codes; verify which module reports the loss
- Check for additional communication codes (other U-codes) that indicate network problems
- Visually inspect door harness, hinge area, and connectors for damage, chafing, corrosion, or pinched wires
- Verify fuses/power supplies feeding the driver door switch assembly
- Verify ground connections for door module/driver door switch assembly
- Check for aftermarket devices or recent repairs that may have disturbed wiring or modules
Signal parameters
- Serial data bus should show active traffic on scan tool when ignition is ON and modules awake
- CAN bus nominal recessive voltage ~2.5 V per bus line (when applicable); single-wire serial lines should show toggling activity when commanded
- B+ supply to door switch assembly: battery voltage (~12 V) present with key/ignition as required
- Ground continuity: near 0 ohms between module ground terminal and chassis ground
- No short to battery or ground on serial data line (low ohms or stuck high/low indicates fault)
Diagnostic algorithm
- Retrieve freeze frame and all stored codes. Note whether code is current or intermittent and other related U-codes.
- Use a scan tool to observe live serial data bus status and verify whether the driver door switch assembly appears on the network or has unique messages.
- With ignition ON, check power and ground at the driver door switch assembly connector. Verify B+ and ground are within specification.
- Inspect the driver door harness in the hinge area for physical damage; flex the door while monitoring communication for intermittent faults.
- Visually inspect and disconnect/reconnect connectors at the door switch assembly and BCM/gateway. Check pins for corrosion, bent pins, or pin retention problems.
- Measure continuity between the door switch assembly and BCM connectors on the serial data circuit and power/ground circuits with the connectors disconnected (ignition off).
- If continuity is good but no data, scope or use a data-line tester to check for signal activity on the serial data line while operating door switches and locking/unlocking. Replace door switch assembly if no activity and power/ground are good.
- If the data line is stuck high/low or shows short to battery/ground, isolate and repair wiring (locate splice or chafe) or replace damaged harness section.
- If wiring and connectors check good but issue persists, test or swap door module (if a known-good unit available) or follow manufacturer procedures for BCM/gateway diagnostics.
- After repairs, clear DTCs and verify repairs by cycling ignition/doors and re-checking for presence of U1170 and proper door switch operation. Reprogram or update module software if required by service information.
Likely causes
- Damaged door harness in the driver door hinge area
- Connector corrosion at the driver door switch assembly
- Blown fuse or lost B+ to door switch assembly
- Failed driver door switch assembly module
- Faulty splice or short to ground/battery on serial data circuit
Fault status
Status
Driver Door Switch Assembly communication lost on vehicle serial data bus. Door functions tied to that module may be inoperative.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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