What is the most common gas/fuel leak? - 1986 Toyota Pickup 4WD

The evaporative (EVAP) emission system is all about controlling fuel vapors. When a leak develops, it allows the vapors to enter the atmosphere which is harmful to the environment. Modern vehicles therefore have been designed with a system to detect when a leak is present. There are several different Diagnostic Trouble Codes (DTCs) than can be set for EVAP leaks including those for very small, small, or gross (large) leaks. The most common gross/large leak is from a loose or damaged fuel cap. Because it's the most common, people often assume that the gas cap is the culprit even though it could be elsewhere in the system. Some vehicles even have a fuel cap indicator light that makes this same assumption. If you have a DTC for an EVAP leak and/or the fuel cap indicator light is on and you've already replaced the gas cap, then an EVAP leak test should be performed to locate the true source of the leak. You can read more about large EVAP leaks and the associated warning indicators here: https://www.yourmechanic.com/article/what-does-the-fuel-cap-warning-light-mean-by-spencer-cates

Get a good mechanic to check the whole fuel supply system!
Is the filler hole that side? Fuel being a liquid can travel along surfaces so where it drips might not be where it's leaking.
The most common reasons for a fuel leak will be-
-a split or punctured fuel line.
-a loose or damaged filler neck joint.
-a loose fuel filter or it's housing.
It will be worth getting the fuel tank itself examined for damage as some older cars still used metal tanks.

P0455 - Evaporative Emission Control (fuel vapor control) System Leak Detected Gross Leak

Possible causes- Missing or loose fuel cap
- Incorrect fuel filler cap used
- Fuel filler cap remains open or fails to close
- Foreign matter caught in fuel filler cap
- EVAP canister or fuel tank leaks
- EVAP system hose leaking
- Fuel tank leaking Tech notes The P0455 it's a very common code, because the code is set if the gas cap is loose or missing. Start by tighten the gas cap and clearing the code. In most cases the code can be clear by disconnecting the car battery for about 30 minutes.

Very common to see rusted and leaking fuel lines.Tanks have also been known to rust and leak

Hi, the code indicates a fuel vapor leak or lack of purge flow in the EVAP control system. It means a large leak has been detected. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

p0455 most likely means one or more of the following has happened:

• A loose or improperly affixed gas cap
• A non-conforming gas cap (i.e. not factory/original brand)
• Other leak or damaged piece in EVAP system

With a p0455, the most common repair is to:

• Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
• Otherwise, replace the gas cap, and/or
• Inspect the EVAP system for cuts/holes in tubes/hoses (you may hear a vacuum noise or smell fuel), repair if necessary

P0172 - Fuel Injection System Too Rich Bank 1 Symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Excessive Fuel Consumption Possible causes - Intake air leaks
- Front Heated oxygen sensor may be faulty
- Injectors may be faulty
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor may be faulty
- Incorrect PCV hose connec Possible solution Dirty air filter of faulty air flow sensor are common causes of the problem.

P0174 - Fuel Injection System Too Lean Bank 2 Symptoms - Engine Light ON (or Service Engine Soon Warning Light)
- Excessive Fuel Consumption Possible causes - Intake air leaks
- Front Heated oxygen sensor may be faulty
- Injectors may be faulty
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor may be faulty
- Incorrect PCV hose connection Possible solution Dirty air filter of faulty air flow sensor are common causes of the problem. Bottom line possible defective Mass airflow sensor and or O2 sensor in cylinder bank number two.

P0174 - Fuel Injection System Too Lean Bank 2 Possible causes - Intake air leaks
- Front Heated oxygen sensor may be faulty
- Injectors may be faulty
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor may be faulty
- Incorrect PCV hose connection Possible solution Dirty air filter of faulty air flow sensor are common causes of the problem. P0171 - Fuel Injection System Too Lean Bank 1 Possible causes - Intake air leaks
- Front Heated oxygen sensor may be faulty
- Injectors may be faulty
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor may be faulty
- Incorrect PCV hose connection Possible solution Dirty air filter of faulty air flow sensor are common causes of the problem.

P0442 - Evaporative Emission Control System Leak Detected (small leak)

This indicates a fuel vapor leak in the EVAP control system. It means a very small leak has been detected. In fact, the leak can be from a hole as small as 0.04" in diameter. The (EVAP) emission control system prevents the escape of fuel vapors from a vehicle's fuel system. Fuel vapors are routed by hoses to a charcoal canister for storage. Later, when the engine is running a purge control valve opens allowing intake vacuum to siphon the fuel vapors into the engine.

Symptoms: You likely won't notice any drivability problems.

Causes: A code P0442 most likely means one or more of the following has happened:
* A loose or improperly affixed gas cap
* A non-conforming gas cap (i.e. not factory/original brand)
* A small leak/hole in a fuel vapor hose/tube
* Other small leak in EVAP system
* Faulty vent o-ring seal

Possible Solutions: with a P0442, the most common repair is to:
* Remove and reinstall the gas cap, clear the codes, and drive for a day and see if the codes come back.
* Otherwise, replace the gas cap, or
* Inspect the EVAP system for cuts/holes in tubes/hoses



P0445 - Evaporative Emission Control System Purge Control Valve Circuit Shorted.
Possible Solutions: with a P0445, the most common repair is to:
* Bad or loss contact wires
* Check harnesses, replace it


Hope helps (remember to rate this).

your gas tank's filler hose is cracked or leaking. Inspect and replace immediately, this is a major fire hazard!

P0401- Exhaust Gas Recirculation Flow Insufficient Dectected
Possible causes - Harness or connectors (EGR volume control valve circuit is open or shorted.)
- EGR volume control valve stuck closed
- EGR volume control solenoid valve
- Dead (Weak) battery
- EGR passage clogged
- Exhaust gas leaks Possible solution - Clean EGR Valve
- Repair EGR harness or connector
- Replaced EGR volume control solenoid valve
- Replaced EGR volume control valve
Code P0171- Fuel Injection System Too Lean Bank 1 Possible causes - Intake air leaks
- Front Heated oxygen sensor may be faulty
- Injectors may be faulty
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor may be faulty
- Incorrect PCV hose connection Possible solution Dirty air filter of faulty air flow sensor are common causes of the problem P0174- Fuel Injection System Too Lean Bank 2 Possible causes - Intake air leaks
- Front Heated oxygen sensor may be faulty
- Injectors may be faulty
- Exhaust gas leaks
- Incorrect fuel pressure
- Lack of fuel
- Mass air flow sensor may be faulty
- Incorrect PCV hose connection Possible solution Dirty air filter of faulty air flow sensor are common causes of the problem.