Encountering a “no communication to scan tool” issue on a 2012 Ford F150 can be a frustrating diagnostic challenge. Recently, a 2012 Ford F150 arrived at our shop exhibiting precisely this problem after undergoing bodywork. This case study details the troubleshooting steps taken and the intermittent nature of the fault, offering insights for technicians facing similar scenarios.
The vehicle was brought to us after body shop repairs involving the left front fender, headlight, and surrounding components. Initially, the body shop attempted to move the F150, using a booster pack or after a battery charge, but the truck displayed erratic electrical behavior – flashing lights and a failure to start. Their scan tool failed to communicate with the Powertrain Control Module (PCM), indicating a blank PCM.
Upon arrival at our facility, we confirmed a dead battery with voltage plummeting to 6 volts upon key-on. Attempts to charge the battery were unsuccessful, leading to battery replacement. Despite a new battery, the “no communication with PCM” issue persisted. Focus then shifted to the PCM power relay. Testing revealed a stuck relay, seemingly with fused contacts. A physical tap on the relay miraculously brought the PCM online. The engine started and ran without issue multiple times.
Confident in a resolution, the body shop retrieved the F150 for reassembly and final detailing. However, the problem resurfaced when attempting to move the truck from the wash bay – it wouldn’t start again. Upon its return to our shop, unusual clicking noises were audible from the transmission and engine areas. Disconnecting the transmission wiring harness and the throttle body eliminated most of the noise, though a faint clicking, possibly from the direct injectors, remained. Crucially, PCM communication was again lost, with communication only possible with the ABS and Transmission modules out of the 21 modules present on the truck.
Extensive electrical diagnostics ensued, focusing on PCM and Body Control Module (BCM) circuits with these modules disconnected. Remarkably, upon reconnecting both the PCM and BCM, communication was restored to all modules, and the truck started and ran normally, consistently. Interestingly, a P0151 (O2 Sensor Circuit Low Voltage Bank 2 Sensor 1) code appeared almost immediately but cleared after a few drive cycles. Persistent Tire Pressure Monitoring System (TPMS) faults, along with warning lights and messages on the instrument cluster, remained.
The intermittent nature of this 2012 Ford F150 communication issue presents a diagnostic puzzle. Could a short circuit, potentially introduced during the bodywork, be intermittently pulling down the PCM? While the truck is currently operating without fault, the fear of recurrence after returning it to the customer is palpable. We are seeking insights and suggestions from the automotive technician community. Has anyone encountered a similar scenario with a 2012 Ford F150 or a comparable Ford model? Any diagnostic tips or potential trouble areas to investigate further would be greatly appreciated as we strive to resolve this perplexing “no communication to scan tool” issue definitively.
