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Chevrolet Master
8,991 Answers
- Posted on Sep 23, 2011
Re: Hi, I'm still having problems with my 1993 chev...
Hi, these codes indicate both the MAP sensor and the EGR valve. You will need to troubleshoot a bit to see exactly what is wrong. It's possible a vacuum leak could cause both of these codes. I have pasted a procedure to check the MAP sensor below using a voltmeter. If you can run this test and tell me the results, it will help to diagnose the problem. You should also check all of the vacuum hoses, including the ones from the intake manifold to the EGR solenoid and from the solenoid to the EGR valve. The run some jumper wires from the battery to the EGR solenoid pins to see if the solenoid clicks open.
TESTINGSee Figures 3, 4 and 5
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Backprobe with a high impedance voltmeter at MAP sensor terminals A and C.
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With the key
ON
and engine off, the voltmeter reading should be approximately 5.0 volts.
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If the voltage is not as specified, either the wiring to the MAP
sensor or the ECM may be faulty. Correct any wiring or ECM faults before
continuing test.
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Backprobe with the high impotence voltmeter at MAP sensor terminals B and A.
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Verify that the sensor voltage is approximately 0.5 volts with the engine not running (at sea level).
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Record MAP sensor voltage with the key
ON
and engine off.
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Start the vehicle.
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Verify that the sensor voltage is greater than 1.5 volts (above the recorded reading) at idle.
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Verify that the sensor voltage increases to approximately 4.5. volts (above the recorded reading) at Wide Open Throttle (WOT).
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If the sensor voltage is as specified, the sensor is functioning properly.
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If the sensor voltage is not as specified, check the sensor and
the sensor vacuum source for a leak or a restriction. If no leaks or
restrictions are found, the sensor may be defective and should be
replaced.
Fig. Fig. 3: Location of the MAP sensor-TBI system shown
Fig. Fig. 4: Probe the terminals of the MAP sensor to check foHi, I'm still having problems with my 1993 chev - jturcotte_2324.gif voltage
Fig. Fig. 5: ManifoldHi, I'm still having problems with my 1993 chev - jturcotte_628.jpge (MAP) sensor wiring diagram
EGR valve:
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