DTC 34

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

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

If this code is not displayed during the third pass of diagnostic codes, the problem is an intermittent failure. To help isolate the problem, manipulate related wiring while observing parameter .0.2. with engine running. If failure is induced, MAP reading will jump from its normal value at idle to within 6 kPa of BARO reading (parameter .0.3).
Code 34 indicates that MAP and BARO signals have close to same value with engine running. This condition can be observed with parameters .0.2 and .0.3 having readings within 6 kPa of each other with engine at idle. With ignition on and engine not running or cranking, both sensors should read same voltage because they are reading atmospheric pressure. As engine begins to turn over, MAP sensor should read manifold pressure. Possible causes of this condition are:
a. MAP hose leak or blockage.
b. Defective wiring or electrical connectors.
c. ECM not properly processing signals.

To diagnose a Code 34, proceed as follows:
1. Start engine, enter diagnostics and display parameters .0.2 and .0.3. Code 34 will be verified by readings within 6 kPa of each other.
2. Inspect MAP hose for blockage or leaks and repair as necessary. If hose is satisfactory, turn ignition on, enter diagnostics and display parameter .0.2. Disconnect MAP sensor and note parameter value.
3. If reading is 17 or greater, then either wiring harness or ECM is shorted. If circuit 432 is satisfactory, short is in ECM or ECM connector.
4. If MAP reading is 14 to 16, check circuit 476-Y for an open and repair as necessary. If voltage between circuits 474 and 476(Y) is 0, then circuit 476(Y) is open. If voltage measured is 5 volts, fault is improper mating of sensor terminals or a faulty MAP sensor.