P1669

What it means

P1669 on a Cadillac means 'ABS Unit Expected'. The engine control module (or powertrain control module) is configured to expect an ABS or brake control unit on the vehicle network, but it did not see the expected communication or data from it. The exact way the module checks for the unit, and whether the cause is on the network or in the ABS unit itself, can vary by model and year.

Symptoms

• ABS warning light on
• Traction control or stability control warning light on
• Traction control or stability system not working
• Check engine light on with P1669 stored
• Possible other communication or ABS codes stored alongside
• Possible poor or unusual brake pedal or traction behaviour on some models

Possible causes

• Wiring or connector fault in the ABS unit's power, earth or data circuits (corrosion, chafing, loose pins)likely
• Blown fuse or poor power or earth supply to the ABS or brake control unitlikely
• Fault inside the ABS or electronic brake control modulepossible
• Communication network fault affecting several modules, such as a shorted or open data linepossible
• Engine or powertrain control module configured for an ABS unit that is not fitted or not compatible (for example after a part swap or incorrect module programming)possible
• Outdated or faulty control module software or calibration, where a service bulletin for the model appliesrare

How to diagnose

1. Read all stored codes from every module and note any ABS, brake or network communication codes, then record the freeze frame data.
2. Check the ABS and related fuses, and inspect the fuse box for corrosion or loose connections.
3. Visually inspect the ABS unit connector, wiring and nearby harness for damage, water ingress, corrosion or previous repair work.
4. Check whether the scan tool can communicate with the ABS module; if it cannot, test the module's power supplies, earths and data line signals against the wiring diagram.
5. Check for other modules that have lost communication to judge whether this is a network fault or an ABS-only fault.
6. Confirm the ABS unit and powertrain module are the correct parts for the vehicle's specification, and check for previous module replacement or reprogramming.
7. Check for applicable software updates or technical bulletins for the specific model and engine.
8. Clear the code after repair and road test to confirm it does not return.

How to fix

• Repair damaged wiring, terminals or connectors in the ABS unit's supply, earth or data circuits.
• Replace any blown fuse after finding and correcting the reason it failed, and restore poor power or earth connections.
• Repair the network fault, such as a shorted or open data line, found during testing.
• Replace or repair the ABS or brake control module if testing confirms it has failed, and program or configure it as required for the vehicle.
• Correct the module configuration or fit the correct specification part if a mismatch is found.
• Update the control module software where an applicable update exists for the vehicle.

Can I keep driving?

This code for other makes

• P1669BuickABS Unit Expected
• P1669ChevroletABS Unit Expected
• P1669GMABS Unit Expected
• P1669GMCABS Unit Expected
• P1669OldsmobileABS Unit Expected
• P1669SaturnABS Unit Expected

Nearby codes

• P1667CadillacReverse Inhibit Solenoid Control Circuit
• P1670CadillacDriver 4