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.
Control Units
The control unit may be tested with a voltmeter. Engine must be at operating temperature. For testing, ignition switch must be "ON" and engine not running. Measure voltage at each terminal and compare values to appropriate Control Unit Testing chart.
| Malfunction | Control Unit Action |
|---|---|
| Water Thermo Sensor | Outputs a constant 176°F (80°C) command |
| Oxygen Sensor | Holds A/F solenoid to duty 20% |
| Vacuum Sensor | Prevents operation of EGR valve; holds A/F solenoid to duty 0% |
| EGR Position Sensor | Prevents operation of EGR valve |
| Terminal/Description | Voltage | Condition |
|---|---|---|
| A/Ignition Signal | 12V | Ignition Switch "ON" |
| B/Battery Power | 12V | Ignition Switch "ON" |
| C/Air Conditioner Signal | 12V | A/C "ON" (all engine speeds) |
| D/Slow Fuel Cut Solenoid | 12V | 2500 RPM, terminals M and O disconnected |
| E, I, N | N/A | Not Necessary to Check |
| F/Air/Fuel Solenoid | O-12V | At idle speed |
| H/Throttle Positioner Solenoid | 12V | At 1700 RPM |
| K/EGR Solenoid | 12V | At 2500 RPM |
| M/ACV Solenoid | 12V | At idle speed |
| N, P, R/Ground | 0V | Ignition Switch "ON" |
| A/O2 Sensor | 0-1V | At idle speed |
| B/O2 Sensor (Sealed) | 0V | Ignition Switch "ON" |
| C/Water Temperature Sensor | 1.2V | At idle speed |
| D/Ground (Water Temp. Sensor) | 0V | Ignition Switch "ON" |
| I/Power Steering Signal | 12V | Power steering "OFF" |
| K, L/Vacuum Switch | 10V | Ignition Switch "ON" |
| M/Neutral & Clutch Switch | 0V | At idle speed |
| O/Idle Switch | 10V | At idle speed |
| Q/Water Thermo Switch | 0V | At idle speed |
Use the Manual With the Right Hardware
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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.
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