1991 Ford Mustang LX 5.0
ECM
KOEO Test
Key On Engine Off Test. Using The Check-Engine Light this Mustang will allow you to use a jump wire and count the check-engine light in the dash. The jump wire (I’d use spades on each end) would connect the STI (test input) with #2 pin on the connector.
The fox Mustang’s EEC IV computer has two connectors for self-testing and located on the driver-side firewall. The large connector contains the self test output (STO) and ground (SIG RTN). The small pigtail is the self test input (STI).
Engine Stalling or Misfiring Erratic engine behavior may also indicate a bad or failing ECM. A faulty computer may cause the vehicle to intermittently stall or misfire. The symptoms might come and go.
1986 - 1993 Mustangs VIP Connector Location File:X.jpg
