Fuel / air
- pump/module and hotwire harness
- return/returnless changes
- injector identity and characterization
- MAF/intake or speed-density strategy
- boost/nitrous and fuel type
1993–2002 · MODIFIED-CAR DIAGNOSIS
Modified-Car Diagnostic Checkpoints
A system-by-system checklist of modifications that can invalidate stock F-body diagnostic assumptions before a good part gets replaced.
APPLICATION: 1993–2002 Firebird / Formula / Trans Am. Use the engine/year-specific diagnostic after identifying the installed configuration.
MODIFIED-CAR / AFTERMARKET EVIDENCE · VERIFY INSTALLED HARDWARE
FPV RULE
VIN tells you what the car was. Diagnose what is installed now.
Factory procedures remain the baseline, but a modification can change the circuit, calibration, hydraulic geometry, airflow path or mechanical load the procedure assumes.
Ignition / controls
- PCM or harness swap
- VATS/PASS-Key bypass or calibration delete
- LT1 distributor/vent configuration
- cam/crank architecture changes
Starting / charging
- battery relocation
- accessory pulley ratio
- electric water pump
- added fans, pumps or audio loads
- alternator changes
Exhaust / O2
- long tubes and sensor location
- O2 extension wiring
- catalyst/Y-pipe configuration
- exhaust leaks
- rear-O2 calibration changes
T56 / clutch
- original T56 vs Magnum-F
- clutch/flywheel
- master/slave/line
- shim and release geometry
- rear gear/tire changes
4L60E / converter
- actual transmission year
- converter and lockup strategy
- calibration
- cooler
- rear gear and tire diameter
Rear / brakes / suspension
- 3- vs 4-channel ABS/TCS
- rear housing and reluctors
- torque arm/panhard
- brake conversion and wheel envelope
- ride height and bump-steer geometry
Oil / cooling
- pan/pickup/baffle/accumulator
- oil cooler
- thermostat plus fan calibration
- electric pump
- aftermarket fan control
Use this checkpoint correctly
A modification is not automatically the fault. It tells you which stock assumptions need to be verified before you interpret the test result.