P2408 - OBD Trouble Code

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Check Engine Light on is usually the major symptom visible for OBD code P2408 error. OBD II fault code P2408 is defined as “Fuel Cap Sensor/Switch Circuit Issue”, and is set when the PCM (Powertrain Control Module) detects that a part of the evaporative emission control system is not functioning as it should.

The gas cap, also known as the fuel filler cap, is a simple but important component that is found on the vast majority of road going cars and trucks. Their purpose is simple; to prevent dirt, debris, and dust from entering the gas tank, as well as providing a reliable seal. The cap also plays an important role in the operation of the vehicle’s evaporative emissions system, which is designed to capture and reuse fuel vapors from the gas tank that would otherwise be released into the atmosphere. Because the cap is frequently removed, every time fuel is added to the vehicle, it can wear out over time and will need to be replaced. Usually a bad or failing gas cap will produce a few symptoms that can alert the driver of a potential issue.

What causes this problem with the Fuel Cap Sensor/Switch Circuit?

• Fuel cap sensor/circuit faulty
• Wiring and connections to the fuel cap sensor/circuit faulty
• Poor electrical connections to the fuel cap sensor/circuit
• PCM failure

1. Engine Control Module - Most of the time it is difficult to intercept the ECM faults and thus must be checked for thoroughly. There can be a problem with the circuit or the software might have malfunctioned. Thus repair, replace or reprogram the component as per requirement.
2. Powertrain Control Module - If the PCM is faulty, it can stores wrong OBD codes and can lead to misdiagnosis. This can happen due to misinterpretation of data received from the various sensors and components which also affects the vehicle’s performance. Thus replace it immediately.
3. Electronic Control Unit – If the ECU is at fault, it will not be able to read the boost converter temperatures correctly leading to underperformance. Thus, replace faulty ECU now!
4. Diagnostic Tool - Choose from our diagnostic tools collection that will come handy to detect and correct the OBD error code.
5. Fuel Cap - If you get an error pointing to the gas cap it means fuel vapors are leaking out of your cap. This means the cap is either cracked or just wasn’t tightened well enough. Thus, replace it now!
6. Fuel Tank Pressure Sensor - Also known as the fuel rail sensor, the fuel tank pressure sensor is an integral part of the evaporative emissions control systems or rather EVAP. The EVAP captures unburned fuel vapors from the fuel tank and reintroduces them into the fuel system. It helps in many ways, most importantly by saving fuel, minimizing environmental pollution, and preventing damage to the engine. The pressure sensor, which is normally positioned inside or on top of the tank, works to detect the pressure in the fuel system, with the end goal of identifying leaks and defective gas caps.

Next important thing you need to know about are the common symptoms for this obd error code P2408 with your fuel volume control.

Common Symptoms

• Check Engine Light On
• Noticeable fuel odour caused by the release of fuel vapours
• Reduced fuel economy

Wish to correct this error code with your vehicle? Do you know what all you should do to make your car free from this code P2408? Well, don’t worry! We are here to guide you.

• Replacement of fuel cap
• Repair and replacement of damaged wiring and connectors in relation to sensor/circuit
• Replacement of fuel tank pressure sensor

Apart from the fuel injector, you might need to undergo few more replacements. You might need ECM, PCM, charcoal canister, fuel cap, emission control system, fuel cap sensor, purge control solenoid, tank pressure sensor and many other parts. Where to get them from? Well, if you want quality parts, then we can prove to be your dream destination.

If you want to easily diagnose this fault code P2408, then all you have to do is to follow the steps which are mentioned below:

Record all fault codes and available freeze frame data for future reference should an intermittent fault be identified later on. Next, inspect the fuel filler cap, and replace it if there is the slightest doubt about its condition and fitment. If the cap is replaced, clear all codes, and operate the vehicle to see if the code returns.

If the fuel filler cap is good, but the fault persists, perform a thorough visual inspection of all wiring and connectors in the control circuit. Look for damaged, shorted, or corroded wiring/connectors, and repair or replace as required.

If the fault persists, consult the manual to determine the location, color-coding, and function of each wire in the control circuit, and perform continuity, resistance, and reference voltage checks on the control circuit. Be sure however to disconnect all control modules before performing continuity checks to prevent damage to the modules. Compare all obtained readings with values stated in the manual. Make repairs as required, and repeat all checks to ensure that all obtained readings fall within the manufacturer’s specifications.

If all wiring, connectors, and the purge valve solenoid check out fine but the fault persists, suspect either a vacuum leak in the system, or a clogged charcoal canister. Both scenarios are equally likely, so if you have not done so at the beginning of the diagnostic procedure, now would be a good time to remove and inspect the charcoal canister for signs of corrosion.

Since the canister is located under the car, close to the fuel tank, there is a good chance that corrosion ad taken hold in it, thus preventing its proper operation. If there is any doubt about the condition of the charcoal canister, or if there is evidence of the canister being clogged or damaged in any way, replace it. Clear all codes, and operate the vehicle to see if the code returns.

If the canister is good, but the fault persists, place the vehicle on a hoist with the engine running, and allow the system enough time to come into operation. If a suitable scanner is available, monitor the live data stream; the canner will indicate when the PCM commands the purge control solenoid to open. However, confirm the reading by listening for an audible “click” as the solenoid cycles.

If a visual inspection dos not reveal vacuum leaks, the system must be double-checked with the aid of a smoke machine. Locate the vacuum supply hose in the system, and connect the nozzle of the smoke machine to it. Allow the system to fill with smoke; as the purge solenoid cycles, smoke will be drawn into the system.

Keep a sharp lookout for smoke that escapes through small, previously undetected leaks. Smoke cannot escape from a smoke-proof system; where you see smoke, there is a leak, so mark the position of the leak for repair. Repair all leaks found with the smoke machine, but rather replace entire lengths of vacuum line between factory-fitted joints and connections, than attempt to repair leaks. Repairs often start leaking soon due to vibration.

If the code returns despite all repair attempts, it is likely that there is an intermittent fault present. Intermittent faults can sometimes be extremely challenging to find and repair, meaning that the fault may have to be allowed to worsen before an accurate diagnosis, and definitive repair can be made.

Common Mistakes When Diagnosing the P2408 Code

Always check for the following components;

• Fuel Tank Sending Unit defects
• Defective or damaged Fuel Tank
• Fuel Tank Pressure Sensor, wiring, or computer faults
• Carbon Canister faults
• Defective Canister Vent Valve which might not open