temp gauge twitches
11-15-2010, 04:59 PM
#2
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
From the 2001 shop manual:
The SCP (Serial Communications Protocol) network is the same as the OBDII bus--I.e. the instrument cluster micro-controller is interpreting a digital message sent by the PCM and then driving the ECT gauge to provide an appropriate readout.
The analog to digital conversion/interpretation of the sensor's output is accomplished by the PCM.
So; it could be that the sensor output signal is intermittent or electrically "noisy", and the PCM is bing confused by the poor signal (you'd really need an oscilloscope to monitor this); or that the physical connections between the instrument cluster and the gauge motor are loose/corroded or otherwise intermittent or noisy. This can be visually inspected by removing and opening up the instrument cluster.
Engine Coolant Temperature Gauge
Engine coolant temperature information is received by the instrument cluster from the PCM over the SCP network. Engine coolant temperatures above 121°C (250°F) will cause the gauge to indicate above the normal band. If the engine coolant temperature information is missing or invalid for five seconds, the temperature gauge will indicate below the cold (C) position.
Engine coolant temperature information is received by the instrument cluster from the PCM over the SCP network. Engine coolant temperatures above 121°C (250°F) will cause the gauge to indicate above the normal band. If the engine coolant temperature information is missing or invalid for five seconds, the temperature gauge will indicate below the cold (C) position.
The analog to digital conversion/interpretation of the sensor's output is accomplished by the PCM.
So; it could be that the sensor output signal is intermittent or electrically "noisy", and the PCM is bing confused by the poor signal (you'd really need an oscilloscope to monitor this); or that the physical connections between the instrument cluster and the gauge motor are loose/corroded or otherwise intermittent or noisy. This can be visually inspected by removing and opening up the instrument cluster.
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