For couple of weeks i suppose when my GP started to fail my GP light sometimes would not illuminate pre and post startup. That is not normal and is not described anywhere in the service manuals.

I think a short circuit or very low resistance on the temperature sensor may cause the lamp not to come on. The colder it is the higher the resistance for that sensor.

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92 e300d2.5t
01 e320
05 cdi
85 chev c10