Code 33
Code 33 is a diagnostic trouble code related to the Manifold absolute pressure sensor circuit on the Pontiac Fiero.
Code 33 indicates that the ECM has detected a manifold absolute pressure sensor signal that represents unusually low vacuum or high manifold pressure.
Overview
The manifold absolute pressure sensor, often abbreviated as MAP sensor, tells the ECM how much pressure or vacuum is present in the intake manifold.
The ECM uses this signal for fuel mixture, ignition timing, load calculation, and drivability control.
Code 33 is set when the ECM detects a MAP sensor problem with an unusual low-vacuum or high-pressure reading. Common checks include the vacuum hose to the MAP sensor, the sensor connector, wiring, and the MAP sensor itself.
Flash pattern
Code 33 is displayed as:
- Three flashes
- Pause
- Three flashes
This represents code 33.
Animated flash pattern:
Meaning
Code 33 usually indicates that the ECM is seeing the MAP sensor signal as too high, corresponding to low intake vacuum or high manifold pressure.
Possible causes include:
- Disconnected MAP sensor vacuum hose
- Leaking MAP sensor vacuum hose
- Faulty MAP sensor
- MAP sensor wiring problem
- Poor connector contact
- Vacuum leak
- Engine running poorly enough to create low vacuum
- ECM input problem
Symptoms
Possible symptoms may include:
- Check engine light
- Poor acceleration
- Poor fuel economy
- Rough idle
- Hesitation
- Stalling
- Rich running
- Black exhaust smoke
- Poor drivability
- Little or no obvious drivability problem
Diagnosis
Basic diagnostic checks include:
- Confirm that Code 33 is present.
- Inspect the vacuum hose from the intake manifold to the MAP sensor.
- Check for a disconnected, cracked, blocked, or leaking MAP vacuum hose.
- Inspect the MAP sensor connector.
- Inspect MAP sensor wiring for damage.
- Check for poor connector contact or corrosion.
- Check for vacuum leaks.
- Check for other stored trouble codes.
- Test the MAP sensor signal if equipment is available.
- Check ECM connector condition if the sensor, vacuum hose, and wiring appear correct.
Vacuum hose
The MAP sensor must receive a correct manifold pressure signal through its vacuum hose. A leaking, disconnected, or blocked hose can cause the ECM to see an incorrect load signal.
Related topics:
Related codes
Related MAP sensor codes include:
- Code 34 - MAP sensor circuit, low voltage or unusually high vacuum/low pressure indication
Notes
Code 33 should not automatically be treated as a failed MAP sensor. The vacuum hose, electrical connector, wiring, engine vacuum condition, and ECM input should also be checked.
If the MAP sensor signal is incorrect, the ECM may calculate engine load incorrectly, which can cause significant drivability problems.