DTC 33

Fig. 24 Manifold absolute pressure sensor & barometric pressure sensor wiring circuit. 1984:

Fig. 25 Manifold absolute pressure sensor & barometric pressure sensor wiring circuit. 1985:

Code 33 indicates that ECM has sensed a condition where manifold absolute pressure (MAP) sensor signal and barometric pressure (BARO) sensor signal should have been same voltage but were not (ignition on, engine not running). Possible causes of this condition are:
a. Defective MAP sensor.
b. Defective BARO sensor.
c. Defective wiring or electrical connectors.
d. ECM not processing signals properly.
To diagnose a Code 33, proceed as follows:
1. Clear codes, then turn ignition off for 10 seconds and on for 10 seconds. Enter diagnostics and read stored codes.
2. If Code 33 is no longer stored, there is no malfunction in the system at this time. If Code 33 is stored as a hard failure, proceed to step 3. If Code 33 is stored as an intermittent, proceed as follows:
a. Disconnect, then reconnect MAP and BARO sensor electrical connectors. Observe parameter .0.2 when reconnecting MAP sensor and parameter .0.3 when reconnecting BARO sensor.
b. If parameter .0.2 displays intermediate values before reaching maximum, replace MAP sensor.
c. If parameter .0.3 displays intermediate values before reaching maximum, replace BARO sensor.
d. If both parameters display maximum value immediately, install new ECM and retest for Code 33.
3. If Code 33 is stored as a hard failure, proceed as follows:
a. Display parameters .0.2 and .0.3 and record values. Code 33 condition will be verified if readings differ by 2 kPa or more.
b. Connect jumper wire between MAP sensor pin A and BARO sensor pin A, and note parameter values.
c. If MAP value moves closer to BARO value, repair open in circuit 476-Y to MAP sensor.
d. If BARO value moves closer to MAP value, repair open in circuit 476-X to BARO sensor.
e. If parameter values do not change, install a new MAP or BARO sensor and compare this sensor's parameter value to those recorded previously. If value is closer to MAP, replace BARO sensor. If value is closer to BARO, replace MAP sensor.