Verifying Repairs For Two-Trip DTCS

Record freeze frame data and note engine operating conditions at time fault first occurred. In case of misfire or fuel trim faults, it will be necessary to approximate conditions in freeze frame record in order to verify repair. Clear DTCs. Drive vehicle according to drive cycle that allows ECM/PCM to monitor the fault. See appropriate monitor under OBD-II DRIVE CYCLES  .

If drive cycle used to verify repair runs catalytic converter monitor, EGR monitor, EVAP system leak monitor, fuel trim monitor or heated oxygen sensor monitor, repair may be verified in one drive cycle by checking readiness test status. Readiness test status is an indicator showing whether monitor has run or not run. If ECM/PCM ran monitor and found no faults, readiness test status will display COMPLETE or READY. Repair is verified.

If ECM/PCM found fault during drive cycle, or monitor did not meet criteria to run, readiness test status will display INCOMPLETE or NOT READY. Perform drive cycle again. The second time drive cycle is run, readiness test status will display COMPLETE or READY whether or not a fault was found. It will be necessary to check for DTCs. If readiness test status does not display COMPLETE or READY after 2 drive cycles, one or both drive cycles failed to meet criteria necessary for ECM/PCM to run monitor.

Other monitor does not have readiness test status because other monitor runs continuously. Manufacturer's MUT-II Scan Tool (MB991502) provides mode 2 (increased sensitivity) and mode 5 (provisional DTCs) functions which allow repairs to be verified after one drive cycle. Generic scan tools may or may not have these functions. If scan tool does not have these functions, perform other monitor drive cycle twice, then check for DTCs.

MUT-II scan tool mode 2 (increased sensitivity) allows single drive cycle testing of emissions related DTCs. Mode 2 commands ECM/PCM to illuminate MIL and set DTC on first occurrence of fault when code set criteria are being met. If MIL does not illuminate during drive cycle, repair is verified. Return to mode 1 (normal) by turning ignition off or reselecting mode 1. When scan tool returns to mode 1, freeze frame data, readiness test status and DTCs are erased.

MUT-II scan tool mode 5 (provisional DTCs) can be used to verify repairs after only one drive cycle by reporting fault as provisional (pending) DTC. Mode 5 is limited to reporting faults related to misfire, fuel system and faults detected by other monitor.