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2008 Chevy trailblazer. Temp gauge will work most of the time and not work sometimes. It will sometimes stay at 100 degrees and sometimes go 1/2 way then go back to 100 degrees and stay there. Other day mil came on p0128. I replaced thermostat last fall. It was triggering p0128 but every time I started truck took forever for temp gauge to go up thermostat stuck open heater core heating up with engine. I don't think it is the thermostat have good heat when stuck at 100 degrees. I hooked up scan tool when stuck at 100 degrees and bidirectional commanded temp gauge and went up all the way with other gauges. On scan tool when gauge didn't work pcm cts showed 195 degrees and instrument panel scan data showed 100 degrees. I am at a loss. Don't know if it is the cluster or cts or wiring or connector. Substituted value look at obd2 generic data? How could I check thermostat opening and closing with scan data? Should I graph with labscope the cts signal wire? Thanks in advance. Joe
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