DTC 33

Chart - Code 33 Mass Air Flow Sensor (Signal Frequency High):

Wiring Diagram for MAP Sensor:

CODE 33 - MANIFOLD ABSOLUTE PRESSURE (MAP) (SIGNAL VOLTAGE HIGH)


Circuit Description:


The Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). The Elecronic Control Module (ECM) receives this information as a signal voltage that will vary from about 1-1.5 volts at idle to 4-4.5 volts at Wide Open Throttle (WOT). A "Scan" displays manifold pressure in volts. Low pressure (high vacuum) reads a low voltage while a high pressure (low vacuum) reads a high voltage. If the MAP sensor fails the ECM will substitute a fixed MAP value and use the Throttle Position Sensor (TPS) to control fuel delivery.


Test Description: Numbers below refer to circled numbers on the diagnostic chart.

1. Code 33 will set when:

-Signal is too high, (kPa greater than 69 kPa with A/C "OFF" or greater than 75 kPa with A/C "ON"), for a time greater than 5 seconds.
-TPS less than l.6%
Engine misfire or a low unstable idle may set Code 33. Disconnect MAP sensor and system will go into backup mode. If the misfire or idle condition remains, refer symptoms to "DIAGNOSIS BY SYMPTOMS - NO TROUBLE CODE STORED".
2. If the ECM recognizes the low MAP signal, the ECM and wiring are OK.


Diagnostic Aids:

If idle is rough or unstable refer symptoms to "DIAGNOSIS BY SYMPTOMS - NO TROUBLE CODE STORED", for items which can cause an unstable idle. An open in CKT 469 or the connection will result in a Code 33. Ignition "ON" engine "OFF", voltages should be within the values shown in the table on the chart. Also CHART C-lD can be used to test the MAP sensor. Refer to "INTERMITTENT CONDITION DIAGNOSIS" in "DIAGNOSIS BY SYMPTOMS - NO TROUBLE CODE STORED".