2017 Mazda MX-5 Rf OBD2 Code B1472 Lamp Headlamp Input Circuit Short to Ground

What the B1472 code means

Vehicles equipped with a Smart Junction Box (SJB) send reference signals to the headlamps controlling on/off functions, headlamps and parking lamps. When the SJB detects that the headlamp switch has been turned to the “on” position and the multifunction switch set to “low beam” position, it routes voltage to the left and right low-beam headlamps.

What causes the B1472 code?

• Failed wiring, terminals or connectors
• Headlamp switch failure
• Lighting control module (LCM) failure
• SJB failure

What are the symptoms of the B1472 code?

Symptoms can include:

• Headlights that will not work on high beams
• Headlights won't come on

How does a mechanic diagnose the B1472 code?

• Using a good quality code reader/scanner, check for any headlamp-related trouble codes. B1696, B1791, B1793 or B2008 may accompany this trouble code.

• A factory wiring diagram will also be necessary for this diagnosis and repair.

• With the ignition in ON position and headlamp switch OFF, use a digital volt/ohmmeter (DVOM) to monitor the SJB's parameter ID's (PIDs).

• If the PID indicates the headlamps as ON, monitor the PIDs from the SJB as you move the headlamp switch through all positions. Ensure that the PIDs agree with factory specs.

• If not, disconnect the headlamp switch. Check the headlamp switch for continuity.

• If headlamp switch checks OK, disconnect the negative battery cable. Measure resistance between the headlamp switch harness side and ground. Resistance should be less than 5 ohms.

• If resistance is high, clear all trouble codes and test resistance between headlamp switch/harness side and ground, pin by pin. Resistance should be under 10k ohms.

• If resistance is high, check the headlamp switch input circuits for an open condition. Measure resistance between the headlamp switch pins and and the SJB. Resistances should be under 5 ohms.

• If resistances are high, check the SJB's output and check the headlamps for a short to voltage. Clear trouble codes and perform a self-test.

• Check the SJB connectors for corrosion, damaged pins, pushed-out pins. Reconnect all SJB connectors and see if the system operates properly. If not, replace the SJB.

Common mistakes when diagnosing the B1472 code

Often, technicians replace the headlamp switch or multifunction switch without running a full set of diagnostic tests first.

How serious is the B1472 code?

A B1472 code can result in headlamps that will only work on low beam setting, work intermittently or may not work at all.

What repairs can fix the B1472 code?

• New headlamp switch
• Repair of wiring and connectors
• Replacement of SJB

Additional comments for consideration regarding the B1472 code

Be certain to use the right DVOM probes while troubleshooting a B1472 code, to avoid damage or failure of parts.

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