Back to 2002 Acura RL
Help
2002 ACURA RL
3.5L V6•AWD•AUTOMATIC•gas
2 active safety recalls on this vehicle — view recalls
Founding sponsor spot is openYour name on every procedure for this vehicle, permanently.Sponsor — $99 →
Repairs0Labor955Torque6236Fluid16DTC1902Battery2Maintenance0Recalls2
C0091high severityChassis

Brake Booster Performance

on 2002 Acura RL 3.5L V6 · AWD

What this code means

The brake booster is not providing adequate assist, detected by pressure sensor or pedal effort monitoring.

Symptoms

  • Hard brake pedal
  • Increased stopping distance
  • Brake warning light on
  • Engine may stall when brakes applied firmly

Common causes

  • Leaking brake booster diaphragm
  • Cracked or disconnected vacuum hose
  • Check valve failure
  • Brake booster control valve stuck
  • Low engine vacuum on turbocharged vehicles

Diagnostic steps

  1. Perform brake booster leak-down test
  2. Check vacuum hose and check valve
  3. Test engine vacuum at idle
  4. Apply brakes with engine off then start engine (pedal should drop)
  5. Check booster operating rod adjustment

Repair notes

Replace brake booster if diaphragm is leaking. Replace vacuum hose or check valve as needed.

🔌 Don't have a code reader?
Any of these will read and clear this code — pick by how deep you want to go.
Budget handheld~$40
ANCEL AD410 →
No-phone-needed handheld — reads, clears, live data, freeze frame.
✓ ANCEL official store
Serious DIY~$100
BlueDriver Pro →
Enhanced codes (ABS, airbag, TPMS) plus repair reports.
SHOP FAVORITE
Shop-grade tablet~$300
Autel MaxiCOM MK808S →
Bidirectional tests, service resets, all systems.
✓ Autel official store
Pro diagnostics$1,500+
Autel MaxiSys MS906 Pro →
Full-system pro platform — topology mapping, ECU coding, the works.
✓ Autel official store
As an Amazon Associate and Autel/ANCEL partner, OLP earns from qualifying purchases — how we link. This never changes the specs we publish.

Other Chassis codes on this vehicle

🔌 Need this data in your app? It's all in the free API →
🔧 Database maintained under the daily editorial review of Chris Hackleman · Master Technician · 20+ years and Jeff Moore · Master Mechanic · 20+ years. Spot an error? Use the Help link above — a human reads every report.
Stuck on this repair? Take it to The Diag Desk — ask a master tech about this exact car → real human answer within 24h, never AI
Share:XRedditFBWhatsAppThreadsEmail
⚠ STILL BEHIND THE PAYWALL
The 2002 Acura RL repair data is incomplete because no one has sponsored it yet. For $99, we generate the full step-by-step procedures, then fact-check them with a second AI pass and your expert review. Your name on every procedure, permanently.
The same data would cost $169/mo from Mitchell1 or $30/year from ALLDATAdiy — and you'd be renting access, not freeing it. Sponsor once, free forever.
Sponsor the Acura RL — $99 →
Building an app?
Free API access to all this data — 10 requests/day, no card required.
Get an API key →
Run a shop?
Manage repairs, estimates, and customers with ShopBase — $249/mo, all features included.
Try ShopBase →