A customer brought their 2014 Dodge Ram into the shop because the Malfunction Indicator Light (MIL) came on and a loose fuel cap message was displayed on the dash.
Case details
The technician found diagnostic trouble code (DTC) P0456 - Evaporative (EVAP) System Small Leak, so he replaced the fuel cap with an OEM part. After replacing the fuel cap, he could not get the DTC to clear.
He smoke-tested the EVAP system extensively but could not find a leak. With his scan tool connected, the technician noticed that the evaporative system integrity monitor (ESIM) never showed "closed" even though a strong vacuum was generated according to the fuel tank pressure sensor (FTPS). When he jumped the ESIM plug, the scan tool read "open".
A resistance test at pin #70 in PCM plug C1 showed infinite resistance. He then used a power probe to evaluate the integrity of the power and ground wires. That observation led to the finding of a crushed/broken signal wire in the wiring harness that was mounted to the frame by the driver-side exhaust manifold.
Confirmed repair
The technician repaired the wire and cleared the DTC. After that, the ESIM read "closed" on the scan tool. He performed a drive-cycle to run the evaporative I/M readiness monitor to completion. Problem Fixed!
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