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

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DTC U3003:16/U3003:17 [EPS CONTROL MODULE]

DTC	U3003:16	Power supply
	U3003:17
DETECTION CONDITION		Power supply voltage malfunction is detected
FAIL-SAFE FUNCTION		Refer to “Fail-safe function table”. (See DTC TABLE [EPS CONTROL MODULE].)
POSSIBLE CAUSE		DTC is stored in PCM Battery malfunction Generator malfunction Fuse (EPS 60A) malfunction Open or short to GND circuit in wiring harness between battery and EPS control module terminal 1A Open circuit in short-code Poor connection at each connector

Diagnostic Procedure

Step	Inspection		Action
1	VERIFY PCM DTC Using the M-MDS, perform the PCM DTC inspection. (See ON-BOARD DIAGNOSTIC TEST [PCM (SKYACTIV-G 2.0)].) Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [PCM (SKYACTIV-G 2.0)].) DTC troubleshooting completed, then go to the next step.
		No	Go to the next step.
2	INSPECT BATTERY Inspect the battery. (See BATTERY INSPECTION.) Is there any malfunction?	Yes	Charge or replace the battery, then go to Step7. (See BATTERY RECHARGING.) (See BATTERY REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)
		No	Go to the next step.
3	INSPECT GENERATOR Inspect the generator. (See GENERATOR INSPECTION [SKYACTIV-G 2.0].) Is there any malfunction?	Yes	Replace the generator, then go to Step7. (See GENERATOR REMOVAL/INSTALLATION [SKYACTIV-G 2.0].)
		No	Go to the next step.
4	INSPECT FUSE CONDITION Is the fuse (EPS 60A) normal?	Yes	Go to the next step.
		No	If the fuse is blown: Refer to the wiring diagram and verify whether or not there is a common connector between fuse and EPS control module terminal 1A. 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. Go to Step7.
5	INSPECT EPS CONTROL MODULE POWER SUPPLY CIRCUIT FOR OPEN CIRCUIT Switch the ignition OFF. Disconnect the EPS control module connector. Switch the ignition ON (engine off). Measure the voltage between EPS control module terminal 1A (wiring harness-side) and body ground. Is the voltage 10 V or more?	Yes	Go to the next Step.
		No	Refer to the wiring diagram and verify whether or not there is a common connector between battery and EPS control module terminal 1A. 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 Step7.
6	INSPECT EPS CONTROL MODULE GROUND CIRCUIT FOR OPEN CIRCUIT OR POOR GROUND Switch the ignition OFF. Disconnect the EPS control module short-code. Measure the resistance between short-code and body ground. Is the resistance 0—1 ohm?	Yes	Go to the next step.
		No	Repair or replace the malfunctioning part, then go to the next step.
7	VERIFY DTC TROUBLESHOOTING COMPLETED Using the M-MDS, clear the DTC from the EPS control module. (See CLEARING DTC [EPS CONTROL MODULE].) Using the M-MDS, perform the EPS control module DTC inspection. (See DTC INSPECTION [EPS CONTROL MODULE].) Is the same DTC present?	Yes	Repeat the inspection from Step1. If the malfunction recurs, replace the EPS control module, then go to the next step. (See ELECTRIC POWER STEERING (EPS) CONTROL MODULE REMOVAL/INSTALLATION.)
		No	Go to the next step.
8	VERIFY NO DTC IS PRESENT Are any DTCs present?	Yes	Go to the applicable DTC inspection. (See DTC TABLE [EPS CONTROL MODULE].)
		No	DTC troubleshooting completed.

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