Optima L4-2.4L (2001)
Temperature Gauge: Technical Service Bulletins
Instruments - False Temperature Gauge Reading
SOURCE: KIA Technician Times Volume 6 Issue 2, 2003
TITLE: False Temperature Gauge Reading
APPLIES TO: Optima 4 Cylinder
SERVICE TIP:
Some 4-cylinder Optima models may show intermittent high temperature gauge readings, although ECT (Engine Coolant Temperature) readings
displayed by Hi-Scan Pro are within normal operating range. This condition occurs most frequently on older and/or higher mileage vehicles. The most
common cause of the condition is a voltage drop across the main ground circuit. Excessive voltage drop is the result of high resistance linked to
degraded ground contact and heat.
The fault can be verified with a standard digital volt/ohm meter (DVOM) using the following procedures:
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Select DC voltage and low scale for DVOM used
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Attach DVOM positive lead to alternator housing and negative lead to negative post of battery
Note: Make certain all DVOM leads are clear of drive belts and pulleys
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Start engine, turn headlights and A/C on and monitor the voltage reading. A normal vehicle will indicate less than 0.1V
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Allow the engine to warm up at idle and monitor DVOM voltage and vehicle temperature gauge. If voltage drop increases (typically to 0.4V or
more) you will see the temperature gauge move toward the hot/overheated zone. If this occurs, perform the following repair:
1. Remove ground G13 underneath air cleaner box and #2 gauge ground wire at upper starter attachment bolt (see photos)
