Determination Procedure

WARNING: This page is about a different car, the 2020 Mazda CX-30. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION:

When disconnecting the connector, verify that there is no looseness, damage, deformation, corrosion, or poor connection of the connector terminals.
When inspecting the DLC-2, touch it with a paper clip or similar thin pin without directly inserting a tester into the terminals.
Disconnect the negative battery cable before performing any work that requires handling of connectors.

ERROR IS DISPLAYED ON VEHICLE IDENTIFICATION (BETWEEN VEHICLE AND VCM-2) SCREEN (US) - DIAGNOSTIC PROCEDURE

Step	Inspection		Action
1	INSPECT DLC-2 GROUND CIRCUIT Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Inspect for continuity between DLC-2 terminal J and body ground. Is there continuity?	Yes	Go to the next step.
1		No	A malfunction has occurred between DLC-2 and body ground. Repair or replace the malfunctioning location.
2	Measure the voltage at DLC-2. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Switch the ignition ON (engine off). Measure the voltage at DLC-2 terminal A. Is the voltage B+?	Yes	Go to the next step.
2		No	A malfunction has occurred between DLC-2 and battery. Inspect the following fuse or wiring harness. F26 7.5 A fuse Wiring harness between DLC-2 terminal A and F26 7.5 A fuse Repair or replace the malfunctioning location.
3	INSPECT CAN LINE BETWEEN DLC-2 AND BODY CONTROL MODULE (BCM) FOR SHORT TO POWER SUPPLY Measure the voltage at DLC-2 terminals F and E. Is the voltage between 1.5-3.5 V?	Yes	Go to Step 5.
3		No	Go to the next step.
4	INSPECT BODY CONTROL MODULE (BCM) FOR SHORT TO POWER SUPPLY Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Disconnect the connector 3 which has body control module (BCM) terminals 3T and 3S. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Switch the ignition ON (engine off). Measure the voltage at DLC-2 terminals F and E. Is the voltage between 0 V?	Yes	Replace the body control module (BCM) because there is a short to the power supply in the body control module (BCM). (See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION (US) .)
4		No	Repair or replace the wiring harness between the body control module (BCM) and DLC-2 because the wiring harness is shorted to the power supply.
5	INSPECT CAN LINE BETWEEN DLC-2 AND BODY CONTROL MODULE (BCM) FOR SHORT BETWEEN CIRCUITS Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Disconnect the connector 3 which has body control module (BCM) terminals 3T and 3S. Inspect for continuity between DLC-2 terminals F and E. Is there continuity?	Yes	Repair or replace the wiring harness between the DLC-2 and body control module (BCM) because the wiring harness is shorted between circuits.
5		No	Go to the next step.
6	INSPECT BODY CONTROL MODULE (BCM) FOR SHORT BETWEEN CIRCUITS Connect the connector 3 which has body control module (BCM) terminals 3T and 3S. Connect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US) .) Switch the ignition ON (engine off). Measure the voltage at DLC-2 terminals F and E. Is the voltage at DLC-2 terminals F and E the same?	Yes	Replace the body control module (BCM) because there is a short to the power supply in the body control module (BCM). (See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION (US) .)
6		No	Go to the next step.
7	INSPECT FOR SHORT TO GROUND BETWEEN DLC-2 AND BODY CONTROL MODULE (BCM) Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION (US)) Inspect for continuity at the following terminals: Between DLC-2 terminals F and body ground Between DLC-2 terminals E and body ground Is there continuity?	Yes	Go to the next step.
7		No	Go to Step 9.
8	INSPECT CAN LINE IN BODY CONTROL MODULE (BCM) FOR SHORT TO GROUND Disconnect the connector 3 which has body control module (BCM) terminals 3T and 3S. Inspect for continuity at the following terminals: Between DLC-2 terminals F and body ground Between DLC-2 terminals E and body ground Is there continuity?	Yes	Repair or replace the wiring harness between the DLC-2 and body control module (BCM) because the wiring harness is shorted to ground.
8		No	Replace the body control module (BCM) because there is a short to the power supply in the body control module (BCM). (See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION (US) .)
9	VERIFY IF MALFUNCTION CAUSE IS OPEN CIRCUIT IN WIRING HARNESS BETWEEN DLC-2 AND BODY CONTROL MODULE (BCM) Inspect for continuity at the following terminals: Between DLC-2 terminal F and body control module (BCM) terminals 3T Between DLC-2 terminal E and body control module (BCM) terminals 3S Is there continuity?	Yes	Because the circuit between the vehicle and VCM-2 is currently normal, go back to the [TROUBLESHOOTING PROCEDURE].
9		No	Any of the following malfunctions may have occurred. Repair or replace the wiring harness because there is an open circuit in the wiring harness between DLC-2 terminal F and body control module (BCM) terminal 3T. Repair or replace the wiring harness because there is an open circuit in the wiring harness between DLC-2 terminal E and body control module (BCM) terminal 3S. Replace the body control module (BCM) because there is a short to the power supply in the body control module (BCM). (See BODY CONTROL MODULE (BCM) REMOVAL/INSTALLATION (US) .)