Code
U1169
HUMMER
U — Network/User
Loss of Communications with MMM
AI status
Completed
Completed
100%
Causes
- MMM module has no power (fused feed open) or poor ground
- Loose, corroded or damaged connector at the MMM
- Open/shorted or short-to-power/ground on the CAN or vehicle data lines
- Missing/failed CAN bus termination or wiring splice failure
- MMM internal failure (hardware or software crash)
- Module asleep or not woken up by vehicle wake-up request
Symptoms
- Scanner shows U1169 and MMM not listed/responding
- Functions controlled by MMM are inoperative or intermittent
- Related modules report network or missing module warnings
- No diagnostic data available from MMM when probed with scan tool
- Possible recurring communication codes or network timeouts
What to check
- Verify battery voltage (engine off and key-on) and charging system health
- Check for other U‑codes indicating network issues or related module failures
- Inspect MMM connector for corrosion, bent pins, or loose terminals
- Check fuses and relay(s) supplying MMM power
- Measure power and ground at MMM connector pins with key ON
- Visually inspect CAN bus wiring harness for damage, chafing, or repairs
Signal parameters
- Vehicle battery voltage: ~12.4–12.8 V engine off, >13.5 V with engine running
- CAN High (recessive): ≈2.5 V; CAN Low (recessive): ≈2.5 V
- CAN High (dominant): ≈3.5 V; CAN Low (dominant): ≈1.5 V (differential ≈2.0 V)
- Termination resistance between CAN H and CAN L: ≈60 ohms (two 120Ω in parallel)
- Wake-up messages on bus are periodic; absence may indicate module asleep or bus-off
Diagnostic algorithm
- Record freeze frame and all present codes; note when condition occurs and any related codes.
- Verify battery and charging system are healthy; recharge/replace battery if low and retest.
- Clear codes and attempt to reproduce U1169 while monitoring for other network codes.
- Visually inspect and secure MMM connectors; disconnect and inspect pins for corrosion/damage.
- With key ON, measure power and ground at MMM connector; if missing, trace fuses/feeds and repair.
- Check CAN bus continuity: measure resistance between CAN H and CAN L at vehicle-level and at MMM—expect ~60Ω.
- Use a lab scope or CAN bus tester to view CAN traffic at the MMM connector. Look for frames, voltage levels, errors, or bus-off state.
- If CAN traffic is present elsewhere but absent at MMM, isolate/repair wiring between MMM and nearest gateway or splice.
- If wiring and power/ground are good but MMM does not respond, try re-programming/re-flashing module software if available and recommended by manufacturer.
- If reprogramming fails and all wiring/power/ground verified, consider replacing the MMM. After repair, clear codes and verify normal bus communication and operation.
Likely causes
- Faulty or loose connector/power/ground at the MMM
- CAN bus wiring fault between MMM and gateway/other modules
- Failed MMM module
- Battery or vehicle low-voltage condition preventing module wake-up
Fault status
Status
Loss of communications with MMM — the MMM module failed to respond on the vehicle communication bus when queried. Network or module-level fault preventing normal communication.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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Code
U1169
Other
U — Network/User
SCP (J1850) Invalid or Missing Data for Primary Id
AI status
Completed
Completed
100%
Causes
- MMM module has no power (fused feed open) or poor ground
- Loose, corroded or damaged connector at the MMM
- Open/shorted or short-to-power/ground on the CAN or vehicle data lines
- Missing/failed CAN bus termination or wiring splice failure
- MMM internal failure (hardware or software crash)
- Module asleep or not woken up by vehicle wake-up request
Symptoms
- Scanner shows U1169 and MMM not listed/responding
- Functions controlled by MMM are inoperative or intermittent
- Related modules report network or missing module warnings
- No diagnostic data available from MMM when probed with scan tool
- Possible recurring communication codes or network timeouts
What to check
- Verify battery voltage (engine off and key-on) and charging system health
- Check for other U‑codes indicating network issues or related module failures
- Inspect MMM connector for corrosion, bent pins, or loose terminals
- Check fuses and relay(s) supplying MMM power
- Measure power and ground at MMM connector pins with key ON
- Visually inspect CAN bus wiring harness for damage, chafing, or repairs
Signal parameters
- Vehicle battery voltage: ~12.4–12.8 V engine off, >13.5 V with engine running
- CAN High (recessive): ≈2.5 V; CAN Low (recessive): ≈2.5 V
- CAN High (dominant): ≈3.5 V; CAN Low (dominant): ≈1.5 V (differential ≈2.0 V)
- Termination resistance between CAN H and CAN L: ≈60 ohms (two 120Ω in parallel)
- Wake-up messages on bus are periodic; absence may indicate module asleep or bus-off
Diagnostic algorithm
- Record freeze frame and all present codes; note when condition occurs and any related codes.
- Verify battery and charging system are healthy; recharge/replace battery if low and retest.
- Clear codes and attempt to reproduce U1169 while monitoring for other network codes.
- Visually inspect and secure MMM connectors; disconnect and inspect pins for corrosion/damage.
- With key ON, measure power and ground at MMM connector; if missing, trace fuses/feeds and repair.
- Check CAN bus continuity: measure resistance between CAN H and CAN L at vehicle-level and at MMM—expect ~60Ω.
- Use a lab scope or CAN bus tester to view CAN traffic at the MMM connector. Look for frames, voltage levels, errors, or bus-off state.
- If CAN traffic is present elsewhere but absent at MMM, isolate/repair wiring between MMM and nearest gateway or splice.
- If wiring and power/ground are good but MMM does not respond, try re-programming/re-flashing module software if available and recommended by manufacturer.
- If reprogramming fails and all wiring/power/ground verified, consider replacing the MMM. After repair, clear codes and verify normal bus communication and operation.
Likely causes
- Faulty or loose connector/power/ground at the MMM
- CAN bus wiring fault between MMM and gateway/other modules
- Failed MMM module
- Battery or vehicle low-voltage condition preventing module wake-up
Fault status
Status
Loss of communications with MMM — the MMM module failed to respond on the vehicle communication bus when queried. Network or module-level fault preventing normal communication.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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Repair manuals
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