Vehicle: 2010 Dodge Grand Caravan, V6-3.3L, Flex Fuel, Automatic Transmission
Problem: The vehicle starts and runs fine, but after 40+ miles, it develops a very intermittent, quick stumble and sets p1128. At times, the customer has driven up over 100 miles and not set a code. The fuel system checked out okay. The tech also checked the wiring for the MAP, O2 & ECT sensors – all were good.
Details: The P1128 DTC indicates the vehicle is taking too long to go into closed loop. Given the lack of associated DTCs for the ECT or O2 sensor performance, the ALLDATA Tech-Assist consultant suspected that the most likely cause was a bad thermostat. It was not allowing the engine temp to rise above 185 degrees Fahrenheit quickly enough. He suggested replacing the thermostat.
Confirmed Repair: The tech replaced the thermostat with an OE unit and replaced the coolant. After road testing the vehicle for 150 miles and six cold starts, the DTC did not come back and all the emissions monitors ran to completion each time.