Equus 3123 - GM Code Reader (1982 - 1995) User Manual
Page 18
2
2-9
GM
CODE
SERVICE CODE DEFINITION
33
Mass air flow (MAF) sensor - signal voltage or frequency
is high during engine idle
Manifold absolute pressure (MAP) sensor - signal
voltage is high during engine idle (Note: Engine misfire
or unstable idle may cause this code)
34
Mass air flow (MAF) sensor - signal voltage or frequency
is low during engine cruise
Manifold absolute pressure (MAP) sensor - signal
voltage is low during ignition on
Pressure sensor circuit - signal voltage too high or low
(carburetor engines)
35
Idle air control (IAC) system problem - can not set
desired RPM or idle speed actuator (ISA) carbureted
system problems
36
Mass air flow (MAF) sensor - burn-off circuit problem
Transmission shift problem (electronically controlled
transmissions only)
Direct ignition system (DIS) fault - loss of 24X signal or
extra or missing pulses in electronic spark timing (EST)
signal
Ignition system fault - loss of High Resolution Pulse
signal
37
Brake switch stuck"on"
38
Brake switch circuit fault
Knock sensor (KS) - open circuit problem
39
Torque converter clutch (TCC circuit fault)
Clutch switch circuit problems
Knock sensor (KS) - short circuit problem
41
Cam sensor (CAM) failure
Cylinder select error
Tach input error - no reference pulses during engine run
Electronic spark timing (EST) circuit - open or shorted
to ground during engine run
Direct ignition system (DIS) fault - bypass circuit open
or shorted to ground during engine run
Ignition system fault - loss of 1X Reference Pulse signal