21/06/2026 6:12 am
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Automotive Q&A
Hot no-start has zero RPM and the crank signal disappears above 92°C
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A 2011 Cruze 1.8 starts cold and runs normally, but after a heat soak it cranks without starting. Scan data shows 0 RPM during the failed attempt. The crank sensor has power and ground, and its signal is clean when cold; near 92°C the waveform becomes erratic and then flat while the cam signal remains present. Cooling the sensor restores the signal.
Is that enough to identify the sensor, or should the harness and control module input still be separated?
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22/06/2026 9:51 am
The temperature correlation is strong, but verify the signal at both the sensor and the control-module pin during the same failure. If the waveform is absent directly at the sensor while its supply and ground remain stable, the sensor is failing. If it exists at the sensor but not at the module, the harness or connector is the fault.
Backprobe without spreading terminals and keep the test leads away from the belt. Record cranking voltage as well, because low system voltage can collapse some sensor signals and imitate a temperature-related failure.
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23/06/2026 9:29 am
During the hot failure, the signal was absent at the sensor output and at the ECM while the 5 V supply stayed at 5.01 V and ground drop was 0.03 V. A new crank sensor maintained a clean waveform through two heat-soak cycles and RPM data remained stable.