DTC 33

CODE 33, MAP/BARO SENSOR CORRELATION

IMPORTANT: The following procedure is designed to account for intermittent codes. If no malfunction is uncovered using this procedure, it will indicate that the DFI system is OK at this time. Refer to "Note on Intermittents".










Code 33 indicates that the ECM has seen a condition where the Manifold Absolute Pressure (MAP) sensor signal should have been the same voltage but were not (ignition on but the engine not running or cranking). Possible causes of this condition are:
A. A faulty MAP sensor.
B. A faulty BARO sensor.
C. Defective wires, terminals, etc.
D. An ECM not processing the signals properly.

1. Begin diagnosis by determining whether the code is hard, intermittent or a sensor response problem. If after 10 seconds at ignition on, the code does not set either as hard code or intermittent, then the malfunction is not present at this time.
2. If Code 33 is stored as a head code after 10 seconds at ignition on, then this condition can be verified by displaying engine data parameters .0.2 and .0.3. The two pressure readings will differ by 2 or more kPa at ignition on. This could be caused by an open in one of the sensor ground circuits. If one of the sensor readings moves closer to the other when the ground circuits (#476-X and #476-Y) are jumpered together, then the circuit to the sensor which changed in value is open.
3. If neither reading moved, one of the sensors is faulty. To determine which sensor to replace, obtain a replacement MAP or BARO sensor and connect it to the appropriate harness connector. Compare this sensor's parameter value to those recorded previously. If the new sensor reads closer to the original reading for the BARO sensor, replace the MAP sensor. If the New reads closer to the MAP sensor, replace the BARO sensor.
4. If code 33 was stored as intermittent after 10 seconds at ignition on, one of the sensor's may be responding too slowly when power is applied. To determine if this is the case, observe each sensor's parametric value as the sensor is reconnected. A good sensor should go to it maximum value. If several values are displayed before the maximum, replace the affected sensor. If both respond properly, the ECM may not be processing the signals properly.

Note on Intermittents: If intermittent Code 33 is being set, manipulate related wiring while observing engine data parameters .0.2 and .0.3. If the failure is induced, one of the pressure sensor readings will change to produce a larger "correlation" difference. This will help to isolate the location of the malfunction.

Code 33 is more difficult to induce if the "outside temperature" reading is not between 50°F and 130°F. The ECM allows for a greater difference between the pressure sensors if this ambient temperature is extreme.