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1998 Sierra 4.3 won't start

MAP Sensor code po108

1998 Sierra 4.3 won't start

Postby esquivelemb [OP] » May 10 2011, 6:38pm

Hello everyone,
New to the site and proud owner of a '98 Sierra,
My truck won't start and my obd2 reader gives me code po108 as an only code, is it posible that the MAP sensor is not letting my truck start ?
Any comment appreciated.
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Re: 1998 Sierra 4.3 won't start

Postby 2005GMCSS » May 10 2011, 7:50pm

In unison with the Manifold Absolute Pressure (MAP) sensor, the engine control module (ECM) regulates the flow of fuel and the ignition timing.
The MAP sensor which is metric pressure enables the ECM to make necessary adjustments for differing altitudes.
The output voltage of the MAP sensor changes with the change in the manifold pressure.
The intake manifold pressure created due to engine load (intake manifold vacuum) and the rpm changes is measured by the MAP sensor and transformed into voltage outputs.
The ECM notes the manifold pressure by keeping a vigil on the MAP sensor output voltage.
The MAP sensor directly receives a 5 volt-reference voltage sent to it by the ECM.
At idle, about 1.0 to 1.5 volts indicates a low-pressure (low voltage) output voltage.
At wide open throttle (WOT) about 4.5 to 4.8 volts indicates higher pressure (high voltage) output voltage. check to see if the map sensor is pluged in . and check connector if bad 9 times out of 10 just replace it
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Re: 1998 Sierra 4.3 won't start

Postby lzn197 » May 10 2011, 8:12pm

No. It probably is low fuel pressure or no spark. If you want, you can unplug the map and the computer will assume a default reading.
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Re: 1998 Sierra 4.3 won't start

Postby 2005GMCSS » May 10 2011, 8:32pm

The MAP sensor directly receives a 5 volt-reference voltage sent to it by the ECM.
At idle, about 1.0 to 1.5 volts indicates a low-pressure (low voltage) output voltage.
At wide open throttle (WOT) about 4.5 to 4.8 volts indicates higher pressure (high voltage) output voltage. the map sensorcould be getting to much or to little voltage
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Firing on 1 cylinder [L1]
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Re: 1998 Sierra 4.3 won't start

Postby esquivelemb [OP] » May 10 2011, 9:26pm

Thank You ! For the responses, I tried unplugging the MAP sensor and still won't turn on.
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Year: 1998
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