Fault Codes/Power Solutions, Inc./DTC-121Power Solutions, Inc.DTC-121UnclassifiedGeneralWhat This Code MeansDTC-121Possible Causes•Lack of continuity between ECT sensor ground pin B and ECM connector pin 49•Lack of continuity between ECT connector signal pin A and ECM connector terminal 31•Damage, corrosion, or contamination on ECM connector pins 31 and 49•Faulty ECMSuggested Actions1Repair the circuit as necessary (refer to Wiring Repairs in Engine Electrical)2Replace ECM3Clear DTC information from the ECM using the DSTRelated Power Solutions, Inc. Fault CodesDTC-131DTC-132DTC-115DTC-135DTC-111DTC-142DTC 653DTC-211DTC 555DTC-241DTC 532DTC-243Browse all Power Solutions, Inc. fault codes→ASK RUDY ABOUT THIS FAULTGet a diagnosis walkthrough for DTC-121 on your specific Power Solutions, Inc. unit — cited to the OEM manual, not a forum guess.Your question about DTC-121GET THE ANSWERFree account required — we'll bring your question with you.