Retrieving Codes
FAULT CODE DEFINITIONS FOR MCU SYSTEMS (11 - 45)
Refer to page 72 for "Fault Code Definitions for MCU
Systems". Use the code definition as a guide and
follow the manufacturer's service procedures in the
vehicle's service repair manual to troubleshoot and
repair faults.
All KOER codes that are received by the Code Reader
during the KOER Self test represent problems that
are present now (at the time the test is performed).
The related vehicle problems that cause these codes to
set must be repaired using the procedures described
in the vehicle's repair manual.
11. After all repairs have been completed, repeat the KOER
Self Test to confirm the repair was successful.
FAULT CODE DEFINITION FOR MCU SYSTEMS CAR &
TRUCK
CODE
FAULT CODE DEFINITION
11
NOTE: "High Altitude" refers to vehicles computer
adjusted for high elevations.
I-4 (All except High Altitude): System OK
I-4 (High Altitude only): Altitude (ALT) circuit is open.
I-6: System OK.
V-6 (All except High Altitude): System OK.
V-6 (High Altitude only): Altitude (ALT) circuit is open.
V-8 (All except High Altitude): System OK.
V-8 (High Altitude only): Altitude (ALT) circuit is open.
12
V-8: RPM out of range (throttle kicker).
25
V-8: Knock Sensor (KS) signal not detected.
33
I-4, I-6, V-6: Key On Engine Running (KOER) Self-Test
not initiated.
41
All Engines: Exhaust Gas Oxygen sensor: voltage signal
lean (low).
42
All Engines: Exhaust Gas Oxygen sensor: voltage signal
rich (high).
44
All Engines: Oxygen sensor signal indicates Rich -
excessive fuel, restricted air intake — or — Inoperative
Thermactor System
45
All Engines: Thermactor air flow going upstream to
exhaust manifold.
71
4
Chapter 4