Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2003 Mazda B2300 Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Pcm Power Relay
- Check VPWR Circuit Resistance - Disconnect Idle Air Control (IAC) valve 2-pin harness connector. Disconnect scan tool from DLC. Disconnect PCM power relay. Measure resistance of VPWR circuit (Red wire) between IAC valve harness connector and PCM power relay connector. If resistance reading is less than 5 ohms, reconnect IAC valve. Go to next step. If resistance reading is 5 ohms or more, repair open in VPWR circuit (Red wire) between PCM power relay and splice to IAC valve. See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, restore vehicle to original condition. Rerun QUICK TEST under SELF-DIAGNOSTIC SYSTEM.
- Check B+ & IGN START/RUN Voltage To PCM Power Relay - Measure B+ circuit (Yellow wire) at PCM power relay connector. Record reading. With KOEO, measure voltage of IGN START/RUN circuit (Tan/Black wire) at PCM power relay connector. Record reading. If both voltage readings are more than 10.5 volts, go to next step. If either voltage reading is 10.5 volts or less, turn ignition off. Repair open in B+ circuit (Yellow wire) or IGN START/RUN circuit (Tan/Black wire), and verify condition PCM diode. After repair, restore vehicle to original condition. Rerun QUICK TEST under SELF-DIAGNOSTIC SYSTEM.
- Check Ground Circuit To Power Relay - Measure voltage between B+ circuit (Yellow wire) and ground circuit (Black/White wire) at PCM power relay connector. Turn ignition off. If voltage reading was more than 10.5 volts, replace faulty PCM power relay. After repair, restore vehicle to original condition. Rerun QUICK TEST under SELF-DIAGNOSTIC SYSTEM. If voltage reading is 10.5 volts or less, repair open in ground circuit (Black/White wire). See appropriate WIRING DIAGRAM under ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS. After repair, restore vehicle to original condition. Rerun QUICK TEST under SELF-DIAGNOSTIC SYSTEM.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
Rather have a pro handle this?
A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.
Comes to youSame-day available12-month warranty
Get a Free QuoteNo obligation. See pricing before you book.