How to manually check for ECM error codes:

Note, if your Firebird does not have the 12 pin DLC connector, you may not be able to manually flash your codes as explained below.
 

       With the ignition OFF, take a paper clip or a small piece of wire and connect pin #6 to pin #12 (on later cars it will be pin #5 to pin #6) then turn on the ignition to the ON position without starting the engine. 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. If your cars stereo requires you to enter a 4 digit code when you do this, the best thing for you to do is to just remove the fuse going to the ECM.

12:) Diagnostic mode / ECM functioning  No reference pulses to ECM.
13:) Oxygen sensor signal problem or loss.
14:) Coolant sensor - High temperature fault.
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 ORTPS 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) ORThrottle switch circuit shorted.
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 voltage.
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.