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Shift indicator flashes randomly

CousinsDR

By CousinsDR
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CousinsDR Enthusiast

CousinsDR

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95 Sierra XC K2500, 250000 miles, trans replaced at 175000 miles by GM dealer. The shift indicator flashes, at times will go out for 1 or 2 minutes, and at times will flicker in any of the seven positions. Truck drives and shifts normally. Is this an indication that the tranny controls is going bad, or is it a possible loose connection? Is this a common problem? Any thoughts or ideas welcome. Thanks

CousinsDR Enthusiast

CousinsDR

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Additional information..... I have noticed that the indicator flickers when the heater fan on "high". With the ac on is when the previously described problem occurs. With the fan in any position other than "high", and the ac off, the indicator acts normally. Do I need to replace the ECM?? Thanks

TBLAZER Enthusiast

TBLAZER

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95 Sierra XC K2500, 250000 miles, trans replaced at 175000 miles by GM dealer. The shift indicator flashes, at times will go out for 1 or 2 minutes, and at times will flicker in any of the seven positions. Truck drives and shifts normally. Is this an indication that the tranny controls is going bad, or is it a possible loose connection? Is this a common problem? Any thoughts or ideas welcome. Thanks

Here is a doc. from GM that may help in diagnosing your truck.

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Document ID# 879248

1999 Chevrolet Chevy K Silverado - 4WD

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Subject: Info - PRNDL Display Reduced Visibility for Approximately One Minute #02-08-42-004 - (04/18/2002)

 

Models: 2002 and Prior Passenger Cars and Trucks

 

with Automatic Headlamp Control and Vacuum Fluorescent PRNDL Indicator Instrument Panel Cluster

 

--------------------------------------------------------------------------------

 

After backing the vehicle out of a garage or dark environment into a daylight environment, the PRNDL display has reduced visibility for approximately one minute.

 

While the vehicle is parked in a dark environment, the sensor for the automatic headlamp/driving lamps senses that it is dark. When the key is turned to the run/start position, the automatic headlamp module will turn all driving lamps, the instrument panel cluster and PRNDL display ON in the nighttime mode. The nighttime mode intensity of the instrument panel lamps and PRNDL display is controlled by the automatic headlamp module and can be dimmed further by the customer using the dimming control of the headlamp switch.

 

When the customer then moves the vehicle from the dark environment into the bright sunlight, it will take approximately one minute before the headlamp control module recognizes this as true daylight and not just a bright overhead street lamp shining on the sensor. The headlamp control module will then turn the headlamps off and restore the instrument panel and PRNDL display to full brilliance.

 

Without the time delay, the automatic headlamp control module would switch to the night mode (turn on all driving lamps, instrument panel lamps and PRNDL display would dim) each time the vehicle was driven under an overpass or other darkened environment.

 

This is a normal condition and no repair should be attempted.

 

Ensure the instrument panel backlighting control is in the full bright position. This will help alleviate the condition.

 

You may demonstrate to the customer what happens by placing a repair order over the automatic headlamp control light sensor, which will cause the automatic headlamp control module to switch to the night mode in approximately one minute. All driving lamps will come ON, the instrument panel backlight will be dim, and the PRNDL display will also dim to the night setting in conjunction with the position of the headlamp switch dimming control. Demonstrate to the customer the variance in the instrument panel backlighting and PRNDL display while adjusting the headlamp switch dimming control to both ends of its allowable range. Advise the customer to keep the headlight switch dimming control in the highest position to allow viewing of the PRNDL display in a bright environment.

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