What Is the P20B9 Code?
Symptoms
Causes
Seriousness
Can I Still Drive?
Diagnose
Difficulty of Inspecting
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This will cover problems surrounding error code P20B9, which pertains to the components making up the reductant heater of diesel engine vehicles. This is part of a catalyst system responsible for reducing toxic exhaust emissions and is a supplement for a NOx trap.
More About the P20B9 Code – Deeper Dive
Many modern diesel vehicles deliver diagnostic engine codes through the OBD-II port. If code P20B9 is displayed, this indicates that there is no detectable voltage in the control circuit of the reductant heater with the “A” designation. This distinction is made when there are multiple reductant heaters in use. Reductant heaters are part of a system that helps lower diesel engine emissions.
Diesel engines require the use of a catalyst system for the reduction of exhaust emissions. This includes NOx traps, exhaust gas recirculation (EGR) systems, and diesel particulate filter/catalytic converters. Despite this, larger diesel engines cannot meet strict federal (U.S.) emission standards without adding a selective catalytic reduction (SCR) system. This injects a diesel exhaust fluid (DEF) into the exhaust to further reduce emissions.
Reductant heaters prevent DEF from freezing during winter. If the powertrain control module (PCM) detects no voltage from the control circuit of the reductant heater A, then a Check Engine Light may light up, and code P20B9 will be displayed upon OBD II diagnosis.
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What Are the Symptoms of a P20B9 Code?
A P20B9 code may result in diminished engine performance, excessive black smoke coming out from the exhaust, and a reduction in fuel economy. This may also make the Check Engine Light turn on.
What Are Some Causes of a P20B9 Code?
Common causes for this code may be due to either a faulty reductant heater, short circuitry of the reductant heater control unit, a bad reductant temperature sensor, a defective SCR controller/PCM, or an error in programming.
How Serious Is the P20B9 Code?
Code P20B9 is considered a severe problem and should be fixed immediately. This may cause the SCR system to be disabled. Damage could also occur if the conditions are not addressed quickly.
Can I Still Drive with a P20B9 Code?
You will still be able to drive with a P20B9 code during warmer seasons but not during winter months. If the DEF freezes, then it will severely damage the DEF tank.
How Easy Is It to Diagnose a P20B9 Code?
You will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and the vehicle manufacturer’s specific diagnostic information to properly diagnose a code P20B9. The easiest way to initially diagnose the problem is to make a visual inspection of the reductant heater system harnesses and its connectors to look for any signs of burns or damage.
How Difficult Is It to Inspect a P20B9 Code?
If the PCM is put into readiness mode or is reset, then a P20B9 code may appear intermittently, making it difficult to diagnose. If this happens, then you may have to wait for the condition to get worse before you get a more accurate diagnosis.
If the code was reset, then look through vehicle information sources to get diagnostic flow charts, connector pin layout charts, and face views, along with testing procedures and specifications for key components. This information is essential to complete the succeeding steps of your diagnosis.
You can use a DVOM to test the reductant heater element being diagnosed. If the heater doesn’t meet the manufacturer’s performance specifications, then it is more likely that it has failed.
Need Additional Help with Your P20B9 Code?
A P20B9 Code error is a serious issue. It will affect your vehicle’s performance and pollute the environment. Seek qualified assistance from certified experts who know how to diagnose and deal with the problem.
Use Kelley Blue Book to find a repair shop in your area. This makes fixing your car easier and more convenient, no matter what the problem may be.
If you are a DIY mechanic who wants to learn more about error codes and how to fix them, then the KBB OBD-II database provides detailed information that could help you better understand your car.
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