|Code||Fault Location||Probable Cause|
|P2495|| EGR Cooler Bypass Bank 1 Position Sensor Circuit High |
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Table of Contents
- What Does Code P2495 Mean?
- Where is the P2495 sensor located?
- What are the common causes of code P2495?
- What are the symptoms of code P2495?
- Get Help with P2495
What Does Code P2495 Mean?
OBD II fault code P2495 is a generic trouble code that is defined as P2495 – “EGR Cooler Bypass Bank 1 Sensor Circuit High”, or sometimes as P2495 – “Exhaust Gas Recirculation (EGR) Cooler Bypass Flap Position Sensor – Bank 1 Circuit High”, and is set when the PCM (Powertrain Control Module) detects an abnormal voltage or current in the signal and/or control circuits of the EGR cooler bypass flap’s position sensor. Note that “Bank 1” refers to the bank of cylinders that contains cylinder #1 on V-type engines.
SPECIAL NOTES: Not all modern engines are equipped with exhaust recirculation systems. On engines that are equipped with VVT (Variable Valve Timing) or VCT (Variable Camshaft Timing) systems, appropriate adjustments to the valve timing under some operating conditions have the same quenching effect on combustion temperatures that introducing exhaust gas into the cylinders has. END OF SPECIAL NOTES.
Exhaust gas recirculation systems have the task of redirecting metered amounts of exhaust gas back into the engine as a quenching mechanism to reduce combustion temperatures to below about 2200 deg F when an engine operates under high-load conditions. As a practical matter, and since oxygen and nitrogen combine at temperatures of about 2200 deg F to form harmful and toxic NOx (oxides of nitrogen), the EGR system feeds small metered amounts of exhaust gas into the cylinders as a means of quenching the combustion flame to a level where NOx cannot form.
We need not delve into the complexities of how EGR technologies and systems are implemented and controlled on different modern engines here, but suffice it to say that (almost) all modern engines have two things in common. The first of these things is that compression ratios have become progressively higher in recent years, and the second thing is that higher compression ratios produce significantly higher combustion temperatures than was the case in previous generations of engines.
While high compression ratios and combustion temperatures increase the efficiency of modern engines, the very high combustion temperatures of most modern engines leave very little room to manage the prevention of NOx by introducing exhaust gas into engines. As a practical matter, the quenching effect of exhaust gas on combustion temperatures diminishes in an almost linear fashion as combustion temperatures increase, and at a critical threshold, introducing exhaust gas into an engine can increase both compression pressures and combustion temperatures to levels that can cause severe engine damage.
One workaround solution to this problem is to cool the exhaust gas considerably before it enters the engine by passing the exhaust gas through a dedicated cooler or heat exchanger. In most designs, the EGR cooler is connected to the engine’s cooling system, meaning that engine coolant is used to maintain the cooler at a near-constant temperature to ensure the effective, consistent, and predictable cooling of the exhaust gas that passes through it while the engine is hot.
However, EGR coolers are also equipped with devices called “by-pass” flaps that are used under some operating conditions to direct the flow of exhaust gas directly into the engine without first passing through the cooler. This strategy is useful to a) decrease engine warm-up times in low to freezing temperatures, and b) to assist in bringing catalytic converters and other exhaust system components into closed-loop operation sooner.
In almost all cases, the by-pass flap is controlled by the PCM, which relies on input data from a dedicated position sensor that monitors the position of the by-pass flap. It should be noted, though, that adding a cooler and by-pass flap to an EGR system adds several layers of complexity to systems that are already prone to failures and malfunctions caused by the nature of exhaust gas. Therefore, cooled EGR systems have several additional sensors that monitor the temperature of the exhaust gas passing through it, as well exhaust pressure, and flow sensors at strategic points in the system.
Moreover, since the operation of the by-pass flap has a direct bearing on the efficiency of the engine under some operating conditions, the PCM monitors both the operation and position of the by-pass flap continuously. Thus, when the PCM detects a defect, malfunction, or abnormal voltage or current in the circuits that are associated with the by-pass flap, it will recognize that it cannot control the by-pass flap effectively, and it will set code P2459 as a result. In some vehicles, The PCM may also illuminate a warning light upon the first detection of a fault, while in others, the fault must be detected multiple times in succession before the PCM will illuminate a warning light.
Where is the P2495 sensor located?
Although this schematic diagram of a typical cooled EGR system (with the EGR cooler by-pass flap circled in green) is greatly simplified for the sake of clarity, the basic layout of this system is representative of the operation of most, if not all cooled EGR systems.
Nonetheless, it should be noted that the actual layout, appearance, and design of EGR system components vary greatly between vehicle makes and models, and this is particularly true in the case of cooled EGR systems that may use multiple sensors that perform multiple different tasks.
Moreover, since trouble code P2495 refers specifically to the EGR cooler by-pass flap’s dedicated position sensor, we strongly recommend that you research the location of this sensor on the affected vehicle thoroughly to avoid confusion and misdiagnoses by testing/replacing the wrong sensor by mistake.
What are the common causes of code P2495?
The most common causes of code P2495 could include one or more of the following-
- Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors in the wiring that is associated with the EGR flap’s actuator
- If the actuator is vacuum controlled, a perforated, split, or dislodged vacuum line/hose could potentially cause this code to set since the PCM may not see the status of the flap’s position sensor
- Excessive buildup of carbon and oil residues around the flap may inhibit the free movement of the flap
- Failed or failing PCM but note that since is an exceedingly rare event, the fault must be sought elsewhere before any control module is reprogrammed or replaced
What are the symptoms of code P2495?
The most common symptoms of code P2495 largely depend on the nature of the failure and the position of the flap when the failure occurred. Below are some symptoms that may or may not occur-
When the flap is stuck in the closed position
If the flap sticks in the closed position, no exhaust gas will pass through the cooler, which could produce the following symptoms-
- Stored trouble code and possibly an illuminated warning light
- On some engines, a failure to cool the exhaust gas before it enters the engine could produce misfire-like symptoms as well as-
- Noticeable increases in fuel consumption
- Varying degrees of power loss may be present at high engine speeds and loads
- Severe engine knocking may be present upon acceleration
- Severe engine damage resulting from engine knocking
- The engine may be hard to start when it is hot, but this is a rare symptom
When the flap is stuck in the open position
If the code was set as the result of an electrical failure, the only symptom will likely be a stored trouble code and possibly an illuminated warning light.
While it is not impossible for noticeable drivability issues to be present when the flap is stuck open, such symptoms will typically only be present when there is a simultaneous failure or issue with the EGR valve itself.
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