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.
1985 Mazda 626 Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Electronic Control Unit (Ecu)
- The ECU may be tested using a voltmeter. Engine must be at operating temperature. For testing, ignition switch must be in "ON" position and engine not running. Measure voltage at each terminal and compare values to ELECTRONIC CONTROL UNIT TESTING chart. See Fig 1 .
- The ECU has a built-in fail safe mechanism. If certain malfunctions occur during vehicle operation, the ECU will automatically initiate a command so driving performance will not be affected. See CONTROL UNIT MALFUNCTION STRATEGY table.
CONTROL UNIT MALFUNCTION STRATEGY
| Malfunction | Command Sent Out |
|---|---|
| Water thermo-sensor | Control unit outputs a constant 80°C (176°F) command. |
| Feed back system | Control unit holds A/F solenoid to duty 20%. (dwellmeter reading: 18°) |
| Vacuum Sensor | Control unit prevents operation of EGR valve, and holds A/F solenoid to duty 0%. |
| EGR position Sensor | Control unit prevents operation of EGR valve. |
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.