Limp Home Function

The limp home function serves as a back-up system in the event of a break in the air mass meter or other system component signals. For example, if the air mass metering filament were broken, the limp home function in the electronic control unit will enable the vehicle to be temporarily driven with the electronic control unit assuming normal operating conditions.
1. Connect multimeter positive lead to green/red wire and negative lead to violet/white wire at the test socket located near the evaporator housing assembly.
2. Start engine. If the system is in the limp home mode, 12 volts should be obtained. A normally functioning system will read less than 1 volt.
3. If battery voltage is obtained across test socket, test air mass meter by verifying hot wire burn off function as follows:
a. Start and operate engine until cooling fan starts to cycle.
b. Disconnect air mass meter assembly from air filter outlet. Visually check unit for restrictions and/or damage. Do not lose O-ring from inlet side of air mass meter.
c. Increase engine speed to above 2500 RPM and switch ignition Off. After approximately 4 seconds, hot wire should glow for 1 second. If not, peel back air mass meter connector boot and connect multimeter positive lead to pin 1 (red/white wire) and negative lead to pin 4 (black wire) and repeat step c. If the ECU and wiring harness are satisfactory, 4 volts should be obtained during the burn off function.
d. Connect voltmeter positive lead to pin 2 (brown/white wire) and negative lead to pin 4 (black wire) of air mass meter electrical connector.
e. Place a jumper wire on the back of air mass meter connector pins 3 and 5, then check for continuity between pins 6 and 7.
f. Connect the jumper wire between pins 5 and 6 at the air mass meter and check continuity between pins 7 and 14 at the ECU connector.
4. If any faults are found and the system is still in the limp home mode of operation, the air mass meter and ECU assemblies should be substituted with known good units one at a time and limp home function test repeated.