Applies to: 2002 Firebird / Trans Am with the LS1, unless a step on this page says otherwise.
2002 starting and electrical diagnosis arranged by the exact symptom, with a test, expected result and next branch at every step.
APPLICATION: 2002 Firebird / Formula / Trans Am / WS6 with 5.7L LS1. The detailed branch logic and numerical values on this page stay with 2002.
START HERE
First name the symptom. A click, no click, slow crank and normal-speed crank/no-start are different electrical trees and should never be blended together.
STEP 1
Identify the exact starting symptom
DO THIS
With a charged battery, reproduce the complaint once: one click/no crank, no click/no crank, or slow crank.
YOU SHOULD SEE
You can place the car into one of those three branches.
PASS → Continue to the matching branch below.
FAIL → If the engine cranks at normal speed but will not run, leave this page for the 2002 crank/no-start tree.
Inspect the battery case and terminals. Verify the cable connectors do not rotate loosely by hand. Battery-test with clean terminal contact. The 2002 battery procedure uses 15 N·m (11 lb-ft) for cable-bolt tightening after service.
YOU SHOULD SEE
Battery passes and both terminal connections are clean, intact and tight.
PASS → Continue to Step 3.
FAIL → Battery or connection fails: repair that first and reproduce the complaint. Starter diagnosis on a weak battery is noise.
Relay clicks: prove power leaves the relay toward the solenoid
DO THIS
With the relay circuit identified from the exact 2002 schematic, use a test light to verify the relay has its power feed and that the starter-solenoid supply side is being energized during START.
YOU SHOULD SEE
The solenoid feed receives the start command.
PASS → If the starter still does not respond and cable/connection tests pass, starter/solenoid becomes supported.
FAIL → Command is missing after the relay: diagnose relay contacts/output wiring and connections.
Relay does not click: split manual and automatic inputs
DO THIS
Manual: verify the clutch-pedal-position input/adjustment. Automatic: verify the park/neutral-position input/adjustment. Also check SECURITY behavior before blaming the ignition switch or BCM.
YOU SHOULD SEE
The required start-enable input is present and SECURITY is not indicating an inhibit.
PASS → Continue upstream through relay control/ignition-switch/BCM logic using the exact 2002 schematic.
FAIL → Bad clutch or P/N input: repair/adjust it. SECURITY/VTD symptom: move to the VTD tree.
SLOW CRANK: test battery, wiring and mechanical drag in that order
DO THIS
Battery-test first. Then voltage-drop starter positive and ground paths while cranking. If those pass, verify the engine/accessory drive is not dragging.
YOU SHOULD SEE
Battery, both high-current paths and mechanical rotation all pass.
PASS → Starter is the remaining supported branch.
FAIL → Any prerequisite fails: repair it and retest cranking speed before buying a starter.
PAGE SCOPELS12002Use this page only for the model-year/application stated here unless another year is explicitly identified in the published material.
Before you start
Confirm the page scope above, then work through the published checks in order. Use the linked exact-test procedure whenever this page sends you to one.
APPLICATIONLS1 2002 Use this page only for the model-year/application stated here unless another year is explicitly identified in the published material.
EXACT TESTS3 full test procedures linked from this path.
WORKFLOWFollow the published checks top to bottom instead of jumping to a part replacement.
Modified car?Check first
This diagnostic path is based on the application shown on this page. If the car has non-stock wiring, calibration, engine-management, fuel-system, cooling-system, security, or other related changes, do not assume the stock path matches the car exactly. Verify the circuit and configuration actually present before using a stock result to condemn a component.
Use this as a quick job-side record while you work through the tree. Record what the car actually does before moving to the next branch.
Your notes stay in this browser on this device. They are not sent to F-Body Parts Verdict.
Ready
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.