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Free to use workshop manual for your 2015+ Mk4 'ND' Mazda MX-5

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DTC U3004:16 [START STOP UNIT]

Description	ACC relay circuit malfunction
Detection condition	Start stop unit detects that the ACC monitor voltage of less than 2.5 V for 1 s or more with the ignition switched to ACC or ON (engine off or on).
Fail-safe	Not applicable
Possible cause	ACC relay malfunction ACC relay circuit malfunction Short to ground in wiring harness between MAIN 200 A fuse and ACC relay terminal D IG2 30 A fuse malfunction MAIN 200 A fuse malfunction Open circuit in wiring harness between battery positive terminal and ACC relay terminal D Start stop unit connector or terminal malfunction Short to ground in wiring harness between ACC relay terminal C and start stop unit terminal 1E MIRROR 7.5 A fuse malfunction Open circuit in wiring harness between ACC relay terminal C and start stop unit terminal 1E Start stop unit malfunction

Diagnostic Procedure

Step	Inspection		Action
1	INSPECT ACC RELAY Switch the ignition off. Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE 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.
		No	Replace the ACC relay, then go to Step 6. (See RELAY LOCATION.)
2	INSPECT ACC RELAY CIRCUIT FOR OPEN CIRCUIT OR SHORT TO GROUND Verify that the ACC relay is removed. Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Measure the voltage at the ACC relay terminal D (wiring harness-side). Is the voltage B+?	Yes	Go to the next step.
		No	Inspect the IG2 30 A and MAIN 200 A fuse. Any fuse is blown: Refer to the wiring diagram and verify whether or not there is a common connector between MAIN 200 A fuse and ACC relay terminal D. 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 a short to ground. Repair or replace the malfunctioning part. If there is no common connector: Repair or replace the wiring harness which has a short to ground. Replace the fuse. Any fuse is damaged: Replace the fuse. All fuses are normal: Refer to the wiring diagram and verify whether or not there is a common connector between battery positive terminal and ACC relay terminal D. 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 Step 6.
3	INSPECT START STOP UNIT CONNECTOR CONDITION Disconnect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Disconnect the start stop unit connector. 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.
		No	Repair or replace the connector, then go to Step 6.
4	INSPECT ACC RELAY CIRCUIT FOR SHORT TO GROUND Verify that the ACC relay is removed. Verify that the start stop unit connector is disconnected. Inspect for continuity between the following terminals (wiring harness-side) and body ground: ACC relay terminal C Start stop unit terminal 1E Is there continuity?	Yes	Inspect the MIRROR 7.5 A fuse. If the fuse is blown: Refer to the wiring diagram and verify whether or not there is a common connector between MIRROR 7.5 A fuse and start stop unit terminal 1E. 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 a short to ground. Repair or replace the malfunctioning part. If there is no common connector: Repair or replace the wiring harness which has a short to ground. Replace the fuse. If the fuse is damaged: Replace the fuse. If the fuse is normal: Refer to the wiring diagram and verify whether or not there is a common connector between ACC relay terminal C and MIRROR 7.5 A fuse. 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 a short to ground. Repair or replace the malfunctioning part. If there is no common connector: Repair or replace the wiring harness which has a short to ground. Go to Step 6.
		No	Go to the next step.
5	INSPECT ACC RELAY CIRCUIT FOR OPEN CIRCUIT Verify that the ACC relay is removed. Verify that the start stop unit connector is disconnected. Inspect for continuity between ACC relay terminal C (wiring harness-side) and start stop unit terminal 1E (wiring harness-side). Is there continuity?	Yes	Go to the next step.
		No	Inspect the MIRROR 7.5 A fuse. If the fuse is damaged: Replace the fuse. If the fuse is normal: Refer to the wiring diagram and verify whether or not there is a common connector between ACC relay terminal C and start stop unit terminal 1E. 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 the next step.
6	VERIFY THAT REPAIRS HAVE BEEN COMPLETED Always reconnect all disconnected connectors. Connect the negative battery cable. (See NEGATIVE BATTERY CABLE DISCONNECTION/CONNECTION.) Clear the DTC for the start stop unit using the M-MDS. (See CLEARING DTC [START STOP UNIT].) Switch the ignition to ACC or ON (engine off or on) and wait for 1 s or more. Retrieve the start stop unit DTCs using the M-MDS. (See DTC INSPECTION [START STOP UNIT].) Is the same DTC displayed?	Yes	Repeat the inspection from Step 1. If the malfunction recurs, replace the start stop unit. (See START STOP UNIT REMOVAL/INSTALLATION.) Go to the next step.
		No	Go to the next step.
7	VERIFY IF OTHER DTCs DISPLAYED Are any other DTCs displayed?	Yes	Repair or replace the malfunctioning part according to the applicable DTC troubleshooting. (See DTC TABLE [START STOP UNIT].)
		No	DTC troubleshooting completed.

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