97 Isuzu Trooper engine light

Old 07-19-08, 06:42 PM
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97 Isuzu Trooper engine light

Have a check engine light on. Went to have it checked at local parts shop and came back as P1391. Which they claim is ignition system though as we know the Isuzu specific code is for G Sensor Performance. So here is my issue, the nearest actual Isuzu dealership is closed on weekends and far away. Getting time off work is impossible. And I so do not want some quasi shadetree tech butchering my ride before he decides he is not qualified to fix it. Been there before.

So what do I need to do to fix this thing myself? Is it still safe to drive the vehicle. I have no current issues aside from the annoying little light being on. Is it strictly part of the 4wd operation?

Thanks for any imput guys/girls. Just do not wish to kill my sole source of transportation ^o^
Old 07-23-08, 05:10 PM
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Circuit Description
The G sensor is a vertical low g-acceleration sensor. By sensing vertical acceleration caused by bumps or pot-holes in the road, the powertrain control module (PCM) can determine if the changes in crankshaft speed are due to engine misfire or are driveline induced. If the G sensor detects a rough road condition, the PCM misfire detection diagnostic will be de-activated. The G sensor at rest output should be between 2.35-2.65 volts (+1G). During a rough road condition, the voltage output can vary between 0.5 volt (-1G) and 4.5 volts (+3G).

Conditions for Setting the DTC

Engine running.
No vehicle speed.
G sensor signal indicates greater than 2.5 volts (+1G) or less than 1.5 volts (0G) for one minute.

Vehicle speed is between 50 km/h and 132 km/h (30 mph and 80 mph).
G sensor signal changes more than .0002 volts each tenth of a second (changing faster than physically possible).
Action Taken When the DTC Sets

The PCM will illuminate the malfunction indicator lamp (MIL) after the second consecutive trip in which the fault is detected.
The PCM will store conditions which were present when the DTC was set as Freeze Frame and in the Failure Records data.
Conditions for Clearing the MIL/DTC

The PCM will turn the MIL "OFF" on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.
A history DTC P1391 will clear after 40 consecutive warm-up cycles have occurred without a fault.
DTC P1391 can be cleared by using the scan tool "Clear Info" function or by disconnecting the PCM battery feed. Reviewing the Failure Record vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

Hope this helps ya,
Old 07-23-08, 05:45 PM
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Thanks for the info. The light is off now. Hopefully it will stay off. Happy day ^o^

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