How to Check Error Codes on a 3rd Generation Camaro or Firebird

How to check for ECM error codes on OBD I equipped Third Generation Camaros and Firebirds:

With the ignition OFF, Go to the Diagnostic Connector (Assembly Line Data Link [ALDL]) under the dash on the right side of the instrument panel, take a paper clip or a small piece of wire and connect pin (A) to pin (B) then turn the ignition to the ON position Don’t Start the Engine.

The Connector should be laid out something like this

G H       M

A – Ground
B – Test Terminal
C – Air Injection
E – Serial Data
G – Fuel Pump
H – Brake Sense Speed Input
M – Serial Data

The “Service Engine Soon” light will flash in the following sequence: flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause

To clear all codes from your ECM, disconnect the negative battery cable at the battery and wait about 30 seconds then reconnect it.

Code Meaning
12 Diagnostic mode / ECM functioning No reference pulses to ECM.
13 Oxygen sensor signal problem or loss.
14 Coolant sensor – High temperature
15 Coolant sensor – Low temperature fault.
16 Battery system over voltage – over
17.1 volts OR Direct ignition system fault.
17 Crank signal circuit shorted (RPM signal problem).
21 TPS (Throttle position sensor)
voltage high.
22 TPS (Throttle position sensor) voltage low OR Fuel cutoff relay
circuit open or shorted to ground.
23 MAT (Manifold Air Temperature)
sensor fault – low temperature OR TPS error.
24 VSS (Vehicle Speed Sensor) circuit fault – loss of signal.
25 MAT (Manifold Air Temperature)
sensor fault – high temperature.
26 Quad driver module circuit fault (3.8L) OR Throttle switch circuit
27 Throttle switch circuit open –
fault in 2nd gear switch.
28 Fault in 3rd gear switch.
29 Fault in 4th gear switch.
31 Turbo over-boost fault OR Canister purge solenoid fault OR Camshaft
sensor circuit fault OR EGR circuit fault OR MAP (Manifold Air Pressure)
sensor circuit shorted – low voltage OR Fuel injector fault OR Park or
neutral switch OR governor malfunction.
32 MAP (Manifold Air Pressure) sensor
circuit open OR EGR fault OR Barometric pressure circuit shorted.
33 MAP (Manifold Air Pressure) sensor voltage low – pressure low/vacuum
high OR MAF (Mass Air Flow) sensor signal low – flow high.
34 MAP (Manifold Air Pressure) sensor
voltage high – pressure high/vacuum low OR MAF (Mass Air Flow) signal
high – flow low.
35 Idle speed cannot be set to desired RPM.
36 MAF (Mass Air Flow) sensor
burn-off circuit failure OR fault in direct ignition system OR Missing
pulses in electronic spark timing signal.
37 MAT (Manifold Air Temperature) sensor high temperature.
38 MAT (Manifold Air Temperature)
sensor low temperature OR brake input circuit failed (brake light
switch) OR fault in torque converter clutch brake switch.
39 Fault in TCC (Torque Converter Clutch) circuit.
41  EST (Electronic Spark Timing)
circuit failure – no distributor pulses OR cylinder select error OR
Tachometer input error.
42 EST (Electronic Spark Timing) circuit grounded OR fault at direct
ignition system OR fault at fuel cutoff relay.
43 TPS (Throttle position sensor) out
of adjustment OR knock sensor signal error OR low voltage at electronic
spark timing control.
44 Oxygen sensor lean error.
45 Oxygen sensor rich error.
46 Fault in VATS (Vehicle Anti Theft System) OR fault at power steering
switch (4 cylinder).
47 Problem at ECM or ECM failure.
48 Misfire diagnosis.
49 MAP (Manifold Air Pressure) sensor
low error – vacuum leak.
51 ECM, PROM, or MEM-CAL failure.
52 ECM or CALPAK failure OR Analog to
digital error OR fault at Quad driver module OR low oil pressure sensor
53 System over voltage – over 17.1 volts OR EGR sensor fault, improper
EGR vacuum OR VATS alert.
54 Low voltage at either fuel pump or
fuel pump relay OR output failure at quad driver module.
55 ECM failure or poor ECM connection OR oxygen sensor failure.
56 Coolant level low OR quad driver B
circuit (3.8L).
58 PASS key fuel enable circuit OR VATS alert.
61 Oxygen sensor failure OR cruise
control vent valve solenoid fault (3.8L).
62 Cruise control vacuum circuit fault (3.8L).
63 MAP sensor voltage high, low
vacuum/open circuit (2.8L) OR EGR flow check (3.8L).
64 MAP sensor voltage low, high vacuum/short circuit (2.8L) OR EGR flow
check (3.8L).
65 Fuel injection circuit fault OR
EGR flow check.
66 A/C pressure switch low pressure OR internal reset of ECM.
67 Cruise control switch failure.
68 Cruise control system fault.
69 A/C pressure switch high pressure.
88 ECM fault, internal reset.
108 PROM checksum error.

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