Applies to: 2002 Firebird / Trans Am with the LS1, unless a step below says otherwise.
This test proves rail pressure. It does not automatically prove the pump is good or bad.
PAGE SCOPELS12002Use this page only for the model-year/application stated here unless another year is explicitly identified in the published material.
Start here
Perform this test exactly as shown, record the result, then use PASS or FAIL to return to the diagnostic tree.
Confirm this page matches the vehicle and symptom before testing.
Gather the tools listed on the page before disconnecting anything.
If a STOP warning appears, do not improvise past it.
After a repair, repeat the failed test before moving on.
PASS — The test result is in range or the commanded function works.
FAIL — The result is outside the expected condition; follow that branch.
STOP — The next step needs information/equipment not safely covered here.
Diagnostic Progress0 steps complete
Diagnostic Workpad
Write down the actual measurement before choosing PASS or FAIL. This keeps one bad assumption from steering the rest of the diagnosis.
Your notes stay in this browser on this device. They are not sent to F-Body Parts Verdict.
Ready
SAFETY
Connect the gauge with the ignition off
DO THIS
Relieve fuel pressure as required, keep ignition sources away and connect the EFI gauge to the rail service fitting with the ignition OFF.
YOU SHOULD SEE
Gauge and fitting are secure with no leakage.
PASS → Continue to pump command.
FAIL → Stop and correct any leak before energizing the pump.
STEP 1
Command the fuel pump and read pressure
DO THIS
Use a capable scan tool to command the fuel pump ON. Bleed air from the gauge if the gauge setup requires it, then read pressure while the pump is running.
YOU SHOULD SEE
55–60 psi (380–410 kPa).
PASS → Pressure is in range. Continue to the retention check.
FAIL → Below 55 psi: enter the low-pressure branch. Above 60 psi: inspect the return/high-pressure branch before condemning the regulator.
STEP 2
Watch what pressure does after the pump stops
DO THIS
Command the pump OFF and leave the gauge connected for one minute.
YOU SHOULD SEE
Pressure may move slightly, then stabilizes instead of continuing to fall.
PASS → Basic pressure and retention pass. Return to the symptom tree that sent you here.
FAIL → The supplied factory branch next isolates the feed side from the return/injector side using proper fuel-line shutoff adapters. Do not pinch a fuel line or improvise an isolation tool.
After a repair: repeat the test that failed before calling the car fixed. Then verify the original symptom is gone.
STAY IN THE CORRECT APPLICATION
2002 LS1: related published paths
These links keep you in the same exact-year engine material where available. Do not carry hard numbers, pinouts or thresholds to another year unless that page explicitly says they are shared.