'94 Grand Cherokee 5.2L, TBI. Has OBD, not OBD-II. The Check Engine Light came on after 10-15 mins running.
Checked error codes using the ignition key method, wondering if I'm reading the flashes correctly? Why would the code 21 be repeated ?
12 | 21 | 27 | 21 | 55
Have not had chance to investigate actual problem further yet.
ps: any advice beyond check O2 sensor, injectors and PCM / injector wiring appreciated in comments. Runs fine till warm, then intermittent low power, surge, as if fuel flow drops, but not a missing. Also intermittent rough running at highway speed in OD, but switch off OD and improves.