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Neal, Mechanic
Category: Car
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Experience:  Auto repair pro and Mechanic on multiple makes.
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96 isuzu rodeo high idle

Customer Question

96 isuzu rodeo high idle, replaced the iac and still same thing... keep getting a p1392 and p1391 codes
Submitted: 5 years ago.
Category: Car
Expert:  Neal replied 5 years ago.


Welcome to JustAnswer, my name is XXXXX XXXXX I'm here to help get your problem resolved. Please feel free to ask follow up questions, it is part of the process, thanks.


The codes are related to G sensors and here is a description, They are dealer only items and the dealer would need to do a diagnostic. The high idle may actually be triggering them as they watch the speed of the crank shaft. I would reccomend a dealer diagnostic to find out what is going on and then decide if you want to fix the problem yourself or have them do it. There is just not enough info for me to point you in the right direction.

Circuit Description
The Gravity (G) sensor is a vertical low-g (gravity) acceleration sensor. By sensing vertical acceleration caused by bumps or potholes in the road, the powertrain control module (PCM) can determine if the changes in crank- shaft 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 conditio, 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 30 mph and 80 mph (50 km/h and 132 km/h).
G sensor signal changes more than .0002 volts each tenth of a second (changing faster than physically possible).

It's mounted in a bracket on the frame .I'm fairly certain it's on the Right rear of your rodeo underneath on the frame rail behind the tire.It's a dealer only item and it should be diagnosed before replacement as there may be a circuit problem and not the sensor itself at fault.

Edited by Neal on 2/12/2011 at 2:52 PM EST
Customer: replied 5 years ago.

so the high idle is caused by the "g" sensor that is located in the right rear of the vehicle mounted to the frame??? that will cause high idle??


Expert:  Neal replied 5 years ago.

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Expert:  Neal replied 5 years ago.
The problem is with no codes related to the high idle I cannot tell you where to start. Normally I would suspect a vacuum leak or the IAC but you have replaced the IAC and if there was a vacuum leak there would be a code showing a lean condition. That is why it may be best to get a diagnostic.

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