DTC B121E:12 [MAZDA ERA-GLONASS CONTROL MODULE]

id0902r6080900

Description	ACC output circuit malfunction
Detection condition	The Mazda ERA-GLONASS control module detected a short to power supply in the ACC output circuit.
Fail-safe function	Not applicable
Possible cause	• ACC relay malfunction • DTCs are stored in the start stop unit. • Mazda ERA-GLONASS control module connector or terminal malfunction • Short to power supply in wiring harness between Mazda ERA-GLONASS control module terminal 1X and ACC relay terminal D • Tuner and amp unit (TAU) connector or terminal malfunction • Short to power supply in wiring harness between Mazda ERA-GLONASS control module terminal 1Z and tuner and amp unit (TAU) terminal 2F • Tuner and amp unit (TAU) malfunction • Mazda ERA-GLONASS control module malfunction

Diagnostic Procedure

Step	Inspection		Action
1	INSPECT ACC RELAY • Switch the ignition off. • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION.) • Remove the ACC relay. (See RELAY LOCATION.) • Inspect the ACC relay. (See RELAY INSPECTION.) • Is the ACC relay normal?	Yes	Go to the next step.
1		No	Replace the ACC relay, then go to Step 8. (See RELAY LOCATION.)
2	VERIFY START STOP UNIT CONTROL MODULE DTCs • Retrieve the start stop unit DTCs using the M-MDS. (See DTC INSPECTION [START STOP UNIT].) • Are any DTCs displayed?	Yes	Repair or replace the malfunctioning part according to the applicable DTC troubleshooting. (See DTC TABLE [START STOP UNIT].)
2		No	Go to the next step.
3	INSPECT MAZDA ERA-GLONASS CONTROL MODULE CONNECTOR CONDITION • Switch the ignition off. • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION.) • Disconnect the Mazda ERA-GLONASS control module connector. (See MAZDA ERA-GLONASS CONTROL MODULE REMOVAL/INSTALLATION.) • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection. • Is the connector normal?	Yes	Go to the next step.
3		No	Repair or replace the connector, then go to Step 8.
4	INSPECT MAZDA ERA-GLONASS CONTROL MODULE POWER SUPPLY (ACC) CIRCUIT FOR SHORT TO POWER SUPPLY • Verify Mazda ERA-GLONASS control module connector is disconnected. • Connect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION.) • Switch the ignition ON (engine off or on) • Measure the voltage at the Mazda ERA-GLONASS control module terminal 1X (wiring harness-side). • Is the voltage 0 V?	Yes	Go to the next step.
4		No	Refer to the wiring diagram and verify if there is a common connector between Mazda ERA-GLONASS control module terminal 1X and ACC relay terminal D. If there is a common connector: • Inspect the common connector and terminals for corrosion, damage, or disconnection and the common wiring harnesses for short to power supply to determine the malfunctioning location. • Repair or replace the malfunctioning location. If there is no common connector: • Repair or replace the wiring harness which is shorted to power supply. Go to Step 8.
5	INSPECT TUNER AND AMP UNIT (TAU) CONNECTOR CONDITION • Switch the ignition off. • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION.) • Disconnect the tuner and amp unit (TAU) connector. (See TUNER AND AMP UNIT (TAU) REMOVAL/INSTALLATION.) • Inspect the connector engagement and connection condition and inspect the terminals for damage, deformation, corrosion, or disconnection. • Is the connector normal?	Yes	Go to the next step.
5		No	Repair or replace the connector, then go to Step 8.
6	INSPECT MAZDA ERA-GLONASS CONTROL MODULE ACC OUTPUT CIRCUIT FOR SHORT TO POWER SUPPLY • Verify that the tuner and amp unit (TAU) and Mazda ERA-GLONASS control module connectors are disconnected. • Connect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION.) • Switch the ignition ON (engine off or on) • Measure the voltage at the Mazda ERA-GLONASS control module terminal 1Z (wiring harness-side). • Is the voltage 0 V?	Yes	Go to the next step.
6		No	Refer to the wiring diagram and verify if there is a common connector between Mazda ERA-GLONASS control module terminal 1Z and tuner and amp unit (TAU) terminal 2F. If there is a common connector: • Inspect the common connector and terminals for corrosion, damage, or disconnection and the common wiring harnesses for short to power supply to determine the malfunctioning location. • Repair or replace the malfunctioning location. If there is no common connector: • Repair or replace the wiring harness which is shorted to power supply. Go to Step 8.
7	PERFORM DTC INSPECTION AND VERIFY IF MALFUNCTIONING LOCATION IS TUNER AND AMP UNIT (TAU) • Switch the ignition off. • Disconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION.) • Always reconnect all disconnected connectors. • Reconnect the negative battery terminal. (See NEGATIVE BATTERY TERMINAL DISCONNECTION/CONNECTION.) • Clear the DTC for the Mazda ERA-GLONASS control module using the M-MDS. (See CLEARING DTC [MAZDA ERA-GLONASS CONTROL MODULE]) • Switch the ignition ON (engine off or on) and wait for 25 s or more. • Perform the DTC inspection for the Mazda ERA-GLONASS control module using the M-MDS. (See DTC INSPECTION [MAZDA ERA-GLONASS CONTROL MODULE]) • Is the same DTC displayed?	Yes	Replace the tuner and amp unit (TAU), then go to the next step. (See TUNER AND AMP UNIT (TAU) REMOVAL/INSTALLATION.)
7		No	Go to Step 9.
8	VERIFY THAT REPAIRS HAVE BEEN COMPLETED • Clear the DTC for the Mazda ERA-GLONASS control module using the M-MDS. (See CLEARING DTC [MAZDA ERA-GLONASS CONTROL MODULE]) • Switch the ignition ON (engine off or on) and wait for 25 s or more. • Perform the DTC inspection for the Mazda ERA-GLONASS control module using the M-MDS. (See DTC INSPECTION [MAZDA ERA-GLONASS CONTROL MODULE]) • Is the same DTC displayed?	Yes	Repeat the inspection from Step 1. • If the malfunction recurs, replace the Mazda ERA-GLONASS control module. (See MAZDA ERA-GLONASS CONTROL MODULE REMOVAL/INSTALLATION.) Go to the next step.
8		No	Go to the next step.
9	VERIFY IF OTHER DTCs DISPLAYED • Are any other DTCs displayed?	Yes	Repair the malfunctioning location according to the applicable DTC troubleshooting. (See DTC TABLE [MAZDA ERA-GLONASS CONTROL MODULE])
9		No	DTC troubleshooting completed.