P0655

P0655 means the PCM detected a fault on the Engine Hot Lamp (or coolant overtemp warning lamp) output control circuit — the dedicated low-side driver that grounds the dash overtemp indicator when ECT exceeds the manufacturer's hot threshold (typically 235-250F). Same control logic as P0650 for the MIL: the PCM grounds the wire to illuminate the lamp, releases it to extinguish, and monitors feedback continuity. P0655 sets on open circuit, short to ground (lamp stuck on), short to power, or cluster failure to acknowledge the CAN engine-hot request. Shop-floor ladder, cheapest first: cycle the key to ON and observe the cluster bulb check — most platforms light the engine-hot indicator briefly at KOEO. If the lamp never illuminates during the bulb check, you've got either a blown bulb, a broken cluster trace, or an open control wire. On CAN-driven clusters, scan the network and verify the cluster sees the lamp-on request from the PCM; if the message arrives but the lamp stays dark, the cluster driver or LED is the problem. Backprobe the discrete lamp wire (where applicable) at the PCM output pin — should read battery voltage with lamp off, 0V with lamp commanded on. Drive the vehicle until ECT crosses 230F and watch the PID; if the PCM commands the lamp on but the cluster never lights, the fault is downstream of the PCM. Expensive-misdiagnosis caveat: P0655 on a GM cluster with multiple lamp faults usually means a cluster solder issue, not a PCM driver issue — same rebuilder fix as P0650 for $75-150 versus a $600 cluster replacement.

Vehicle-specific patterns: 2007-2014 GM full-size trucks and SUVs (Silverado, Sierra, Tahoe, Yukon, Suburban) commonly throw P0655 alongside P0650 from the same cluster solder-joint failure pattern — when the cluster's lamp driver bank cracks, multiple lamp-control codes set together. 2004-2010 Ford F-150 / Expedition with the gauge cluster throws P0655 from cluster IC failure or from a broken engine-hot bulb socket. 2003-2009 Dodge Ram throws P0655 from gauge-cluster solder failures at the hot-lamp driver IC. Any vehicle with a missing bulb-check on the temperature warning indicator at KOEO is a primary P0655 candidate. Estimated repair: $75 (cluster rebuild) to $700 (cluster replacement + programming).