Code
P1669
HUMMER
P — Powertrain
ABS Unit Expected
Views:
UK: 7
EN: 19
RU: 9
AI status
Completed
Completed
100%
Causes
- ABS control module not present, not powered, or failed
- Loss of CAN/communication between ABS module and other modules
- Blown ABS fuse or faulty relay supplying module power
- Poor or corroded ground or power connections at ABS module
- Incorrect replacement ABS module that is not programmed or not compatible
- Damaged wiring harness or connector (open, short, high resistance)
Symptoms
- ABS warning lamp illuminated (often with traction control/stability lamp)
- Loss of ABS and possibly traction/stability control functions
- Brake system may revert to non‑ABS braking (longer stopping distance under anti‑lock conditions)
- Multiple communication or ABS‑related trouble codes stored
- No ABS module present in full system scan or module shows 'not responding'
What to check
- Connect a scan tool capable of factory/SAE diagnostics; read DTCs and module presence list
- Check diagnostic trouble code freeze frame and history for related U/C codes
- Verify ABS fuse(s) and relay(s) for proper continuity and operation
- Visually inspect ABS module connector(s) for corrosion, bent pins, or water damage
- Verify battery voltage at key ON and cranking, and check dedicated ABS module +12V and ground circuits
- Check CAN bus communication: confirm ABS module appears on network and compare with other modules
Signal parameters
- Battery supply to ABS module: ~12 V (key ON), >11 V during cranking
- Module ground: close to 0 V with good continuity
- CAN bus idle voltages at connector (key ON): CAN_H ~2.5–3.5 V, CAN_L ~1.5–2.5 V (differential ~0 V idle, ~2 V dominant)
- Dominant vs. recessive bus behavior: expect differential switching during network traffic
- Wheel speed sensor signals (if present): pulsed square/AC waveform with frequency proportional to wheel speed; ~0 Hz at rest
- ABS module diagnostic response: module should respond to scan tool requests within seconds of key ON
Diagnostic algorithm
- Use a capable scan tool to confirm P1669 and list any U‑codes or C‑codes. Note module presence and network health.
- Check ABS module power and ground circuits: confirm fuses, relays, and measure +12 V and ground at the ABS connector with key ON.
- Visually inspect ABS module connectors and harness for corrosion, water intrusion, damaged insulation, and repair as needed.
- Backprobing: with key ON, measure CAN_H and CAN_L at ABS connector; compare to CAN at another known module to detect open/short condition.
- If CAN voltages are abnormal, isolate by disconnecting nearby modules/branches and rechecking to locate short or open segment.
- If power/grounds and CAN are good but module does not respond, attempt reseating connector and clearing codes; re-scan to see if module initializes.
- If module is non‑responsive and wiring is good, verify module part number and programming status. Check for required reprogramming or VIN coding.
- Replace ABS module only after confirming wiring/power and reprogram new unit as required. After repair, clear codes and perform a road/functional test to confirm proper ABS operation.
- If intermittent, perform wiggle tests on harness while monitoring communication and look for diagnostic data or return of codes.
Likely causes
- Blown ABS power fuse or relay preventing module initialization
- Faulty ABS module that fails to boot or communicate on CAN
- Broken CAN bus wiring near ABS module or a short to battery/ground
- ABS module removed or aftermarket unit fitted without proper programming
Fault status
Status
ABS control module expected on CAN network but not detected or not responding. Check module power/grounds, CAN communication, connectors, and module programming.
Repair difficulty: Medium
Diagnostic time: 1.0-4.0 hours
Similar codes
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email