DTC

C1A77:12/C1A77:13/C1A77:16

Valve relay

DETECTION CONDITION

• C1A77:12

• Valve relay in DSC HU/CM stuck ON when the ignition is switched ON, valve relay OFF is commanded.

• C1A77:13/C1A77:16

• Valve relay in DSC HU/CM stuck OFF when valve relay ON is commanded.

FAIL-SAFE FUNCTION

• Illuminates the ABS warning light, brake system warning light, TCS/DSC indicator light, and master warning light*¹.

• Inhibits the ABS, EBD, brake assist, TCS, Hill Launch Assist (HLA), vehicle roll prevention function*², DSC, Mazda Radar Cruise Control (MRCC)*², and Smart City Brake Support (SCBS)*² controls.

*¹: Vehicles with Smart City Brake Support (SCBS).

*²: If equipped.

POSSIBLE CAUSE

• Malfunction of fuse (ABS/DSC S 30A)

• Open circuit in harness between DSC HU/CM terminal AG and battery positive terminal

• Open circuit or short of valve relay in DSC HU/CM

• Stuck valve relay in DSC HU/CM

STEP

INSPECTION

ACTION

1

• Is DSC fuse (ABS/DSC S 30A) normal?

Yes

Go to the next step.

No

Replace the fuse, then go to Step 3.

2

• Switch the ignition off.

• Disconnect DSC HU/CM connector.

• Switch the ignition ON (engine off).

• Measure voltage between DSC HU/CM terminal AG (harness-side) and ground.

• Is voltage B+?

Yes

Go to the next step.

No

Refer to the wiring diagram and verify whether or not there is a common connector between battery positive terminal and DSC HU/CM terminal AG.

If there is a common connector:

• Determine the malfunctioning part by inspecting the common connector and the terminal for corrosion, damage, or pin disconnection, and the common wiring harness for an open circuit.

• Repair or replace the malfunctioning part.

If there is no common connector:

• Repair or replace the wiring harness which has an open circuit.

Go to next step.

3

• Reconnect all disconnected connectors.

• Clear the DTC from the memory.

  (See ON-BOARD DIAGNOSIS [DYNAMIC STABILITY CONTROL (DSC)])

• Is same DTC present?

Yes

Replace DSC HU/CM, then go to the next step.

(See DSC HU/CM REMOVAL/INSTALLATION.)

No

Go to the next step.

4

• Is there any other DTC present?

Yes

Go to the applicable DTC inspection.

(See ON-BOARD DIAGNOSIS [DYNAMIC STABILITY CONTROL (DSC)].)

No

Troubleshooting completed.