What does it mean?
This is a generic powertrain diagnostic trouble code (DTC) applicable to all turbocharged vehicles. Vehicle brands may include, but are not limited to, VW, Dodge, Mercedes, Isuzu, Chrysler, Jeep, etc.
The Powertrain Control Module (PCM) monitors boost pressure with a sensor called the Manifold Absolute Pressure (MAP) sensor. Understanding how a MAP sensor works is the first step in explaining the cause of P0237.
The PCM sends a 5-volt reference signal to the MAP sensor, and the MAP sensor returns a variable voltage signal to the PCM. When boost pressure is high, the voltage signal is high. When boost pressure is low, the voltage is low. The PCM uses the boost control solenoid to control the amount of boost pressure produced by the turbocharger while using the boost pressure sensor to verify that the boost pressure is correct.
This code is set when the PCM detects a low voltage signal indicating low boost pressure when a high-pressure command has been sent to the “A” boost control solenoid.
Symptoms
Symptoms of a P0237 code may include:
Check Engine Light will be illuminated
Low engine power
Reduced fuel economy
Due to the increased risk of damage to the catalytic converter and turbo overboost when P0237 is present, it should be repaired before continuing to use the vehicle.
Causes
Causes
Possible causes for this code being set are as follows:
Faulty “A” boost sensor
Faulty turbocharger
Faulty PCM
Wiring issue
Diagnostic and Repair Procedures
Before diagnosing P0237, ensure no other fault codes are present in the PCM’s memory. If there are other DTCs present, they should be checked first. Any codes related to wastegate control or the 5-volt reference will induce the conditions necessary to set this code. In my experience, the PCM is the least likely cause of this issue. More often than not, it is chafed or burnt wires near the turbocharger causing shorts or opens in the circuit.
A good starting point is always to check the Technical Service Bulletins (TSBs) for your specific vehicle. Your problem may be a known issue with a known fix published by the manufacturer and can save you time and money during diagnosis.
A thorough visual inspection is crucial when trying to resolve this particular DTC. I have seen faulty connections or faulty wiring be the root of the problem more than anything else. Disconnect the connectors for the “A” boost sensor and the “A” boost control solenoid and carefully inspect the contact terminals (the metal parts inside the plastic plug) for signs of spreading. Use a silicone dielectric compound on all connections during reassembly.
Turn the ignition key with the engine off (KOEO), probe the boost sensor reference wire at the sensor connector with a digital voltmeter (DVOM) for a 5-volt check. If the voltage is correct, the boost sensor signal wire should be between 0.2 volts and 0.5 volts. If it is correct, proceed to the next step; if not, suspect a faulty boost sensor.
Leave the DVOM connected and start the engine, and using a hand vacuum pump, apply vacuum to the turbocharger wastegate vacuum motor. The voltage should increase; if it does, suspect a faulty PCM; if not, suspect a faulty turbocharger.