View source for Code 33

'''Code 33''' is a [[Diagnostic trouble codes|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:'''

[[File:Code33.gif|none]]

== 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:

* [[Vacuum leaks]]
* [[MAP sensor]]
* [[Manifold absolute pressure sensor]]

== 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.

== See also ==

* [[Diagnostic trouble codes]]
* [[ALDL diagnostics]]
* [[Manifold absolute pressure sensor]]
* [[MAP sensor]]
* [[Vacuum leaks]]
* [[ECM]]
* [[Fuel system]]
* [[Electrical system]]
* [[Code 34]]

[[Category:Fieropedia]]
[[Category:Diagnostics]]
[[Category:Electrical system]]
[[Category:Engine]]