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.
1986 Models
Code 34 indicates the ECM has seen the following:
- Pressure outside a specified voltage range (seen by ECM as voltage at terminal "20").
- Engine RPM less than a given value.
- Engine at operating temperature.
- All the above for a time greater than specified.
- This tests output of sensor at idle to determine if sensor is within specification. Normal sensor will read .59-.64 volts with key in the "ON" position and engine not running.
- Signal voltage should read over 2 volts with engine idling with a minimum of 15 in. Hg vacuum.
- If voltage reads between 4-6 volts, VAC sensor is faulty.
- Low voltage indicates a faulty circuit 416.
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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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