Code
P1601
HUMMER
P — Powertrain
Serial Comm. Problem With Device 1
AI status
Completed
Completed
100%
Causes
- Open, shorted or damaged communication bus wiring (CAN/LIN/serial)
- Poor connector contacts or corrosion at the module or harness
- Failed or intermittent power supply or ground for Device 1
- Failed Device 1 module (internal electronics)
- Missing or incorrect module programming/software mismatch
- Blown fuse or faulty ignition-switched power to the network
Symptoms
- Malfunction Indicator Lamp (MIL) or warning message illuminated
- Loss or intermittent loss of the specific function(s) tied to Device 1 (refer service manual for mapping)
- Related systems showing faults or degraded performance
- Multiple communication-related DTCs present
- Intermittent or no communication visible on a scan tool for Device 1
What to check
- Read all stored codes and freeze frame data with a scan tool; note timestamps and related U-codes
- Identify which physical module is mapped as “Device 1” in the vehicle service information
- Visually inspect connectors, pins and harnesses for damage, corrosion, rodent chew, or water intrusion
- Check battery voltage and charging system; ensure stable supply during testing
- Check fuses and ignition-switched power circuits for the affected module
- Use scan tool to monitor bus messages and verify whether Device 1 is reporting
Signal parameters
- CAN bus: typical voltages at rest are around CANH ≈ 2.5–3.5 V and CANL ≈ 1.5–2.5 V (differential ~0–1.5 V depending on state) — values depend on vehicle
- Differential resistance across CANH–CANL with ignition on (bus awake) typically ~60 ohms (two 120 Ω terminators in parallel)
- LIN bus: single-wire idle normally near battery voltage; wake and data are pulled low by master/device
- Exact voltage and resistance targets vary by model — consult factory service data for precise values
Diagnostic algorithm
- Verify and record P1601 and any other communication codes with a capable scan tool. Note whether code is current or historical.
- Consult the vehicle service manual to identify which module is labeled “Device 1” and review wiring diagrams for that module’s power, ground and bus connections.
- Perform visual inspection of device connectors and harness; repair damaged insulation, pins, or corrosion as needed.
- Check battery voltage and ground integrity; verify module supply and ground pins have expected voltage with ignition in proper position.
- Check fuses and relays supplying Device 1; replace or repair if faulty.
- With ignition on, check for presence of Device 1 on the vehicle bus with a scan tool. If no messages, measure CANH/CANL (or LIN) at the module connector and at known good node to locate open/short.
- Measure resistance across CANH and CANL (with ignition off) to confirm ~60 Ω; if open or shorted, isolate section by disconnecting connectors and retesting.
- If bus voltages and wiring check good, perform an oscilloscope capture of the network while attempting communication to look for noise, missing frames or corruption.
- Disconnect Device 1 and check if the rest of the bus recovers or if the code changes — careful: some vehicles drop to limp modes when critical modules are disconnected. Follow safety procedures.
- If wiring, power and grounds are good and Device 1 remains non-communicative, consider module replacement or reprogramming per factory instructions.
- After repair, clear codes and perform drive cycle or network test to confirm DTC does not return.
Likely causes
- Loose or corroded connector at Device 1
- Damaged wiring or chafed harness on the communication pair to Device 1
- Failed Device 1 module
- Loss of module power or ground (blown fuse, poor connection)
- Recent module replacement or software update requiring reprogramming
Fault status
Status
Controller detects missing or corrupted serial data from Device 1. Communication messages expected from that device are not being received or fail validity checks. Investigate network wiring, power/ground, connectors, module health and software.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Repair manuals
Manual library for HUMMER
138
Browse 138 HUMMER manuals: repair procedures, diagnostics, wiring diagrams, component locations, service data and Labor Times by year, model and trim.
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