P0237 – Manifold absolute pressure (MAP) sensor A, TC system low input

Reinier

By Reinier (Contact Me)
Last Updated 2017-11-06
Automobile Repair Shop Owner

Trouble CodeFault LocationProbable Cause
P0237 Manifold absolute pressure (MAP) sensor A, TC system low input Wiring short to earth, MAP sensor, ECM

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What Does Code P0237 Mean?

OBD II fault code P0237 is a generic code that is defined as  ”Manifold absolute pressure (MAP) sensor “A”, TC system low input”, and is set when the PCM Powertrain Control Module) detects an abnormally low reading from the turbocharger boost pressure sensor. Note that on some applications, the turbocharger boost pressure sensor and its circuit may be labelled with a letter other than “A”, since there is no set rule or convention regarding the labelling of sensors.

On most applications, the turbocharger boost pressure sensor is a pressure sensitive sensor whose resistance changes as the boost pressure changes. This sensor is usually supplied with a 5-volt reference voltage by the PCM; as the boost pressure changes, the resistance of the sensing element changes in direct proportion to the change in pressure. The changing resistance causes more or less current to pass through the sensor, which changes in the reference voltage are then transmitted back to the PCM via a dedicated signal circuit.

The PCM interprets the signal voltage as pressure, and should the signal voltage fall below a predetermined minimum allowable value, the PCM recognizes that it cannot control the boost pressure effectively, and it will set code P0237 and illuminate a warning light as a result. Note that in the case of code P0237, the minimum allowable pressure value is usually 9 PSI (or more) less than the minimum allowable value set by the manufacturer.

Where is the P0237 sensor located?

On most applications, the sensor is located on the inlet manifold, although there is no set location for the turbocharger boost pressure sensor. Always refer to the manual for the affected application to locate and identify the turbocharger boost pressure sensor correctly, since there may be several other pressure sensors located on, in, or near the inlet manifold.

The image below shows a typical turbocharger boost pressure sensor, but be aware that the appearance, construction, and wiring connectors of these sensors vary widely between manufacturers.

What are the common causes of code P0237 ?

Some common causes of code P0237 could include the following-

  • Defective turbo charger boost pressure sensor
  • Damaged, shorted, burnt, disconnected, or corroded wiring and or connectors
  • Damage to, or leaks in the inlet tract through which boost pressure can be lost
  • Clogged or dirty air cleaner element
  • Defective turbo waste gate, or defects in the waste gate control system that can cause boost pressure to be lost
  • Major leaks in the exhaust manifold that reduce turbo drive pressure
  • Mechanical failure of one or more internal turbo charger components
  • Failed or failing PCM. Note that control module failure is a rare event, and the fault must be sought elsewhere before any control module is replaced

How expensive is it to fix code P0237 ?

If only the boost sensor is to be replaced on a DIY basis, the repair should not cost more than around $200. Note however that this estimate does not include labor charges or relevant fees and taxes if the repair is to be performed by a repair shop, most of which will add a minimum one-hour labor charge to the cost of the part to replace this sensor.

Other repairs depend on the nature of the failure and the application. Note though that the cost of replacing a turbo charger can run to several thousand dollars.

What are the symptoms of code P0237 ?

Some common symptoms of code P0237 could include the following-

  • Stored trouble code and an illuminated warning light
  • Other codes, such as knock sensor, and other turbo charger boost control related codes may be present
  • Mechanical noises from the turbo charger may be present
  • In cases of turbo charger failure, spark plug fouling may occur repeatedly until the problem is resolved
  • Hissing, whistling, or “wheezing” noises may be present, particularly at high engine speeds
  • Depending on the nature of the problem, moderate to severe power loss may be present
  • Serious driveability issues such as poor acceleration, hesitation upon acceleration, frequent stalling, or severe misfires upon acceleration may be present
  • If fitted, the turbo charger boost control gauge may display abnormally low boost pressures

What are common solutions to code P0237 ?

Solutions to code P0237 commonly include the following-

  • Replacement of the boost pressure sensor
  • Inspection and replacement of the air cleaner element
  • Inspection and replacement of damaged wiring and or connectors
  • Inspection and repair of leaks in the inlet tract
  • Inspection and removal of obstructions and restrictions from the inlet tract
  • Repair of leaks in the exhaust manifold
  • In rare cases, repair and/or replacement of a failed/damaged  turbo charger

How serious is code P0237 ?

Apart from the fact that serious driveability issues may develop if this code is nor resolved in a timely manner, serious, if not always fatal damage to both the engine and turbocharger could occur if the low boost pressure is the result of mechanical failure of the turbo charger.

How safe is it to still drive the car with code P0237 ?

Ideally, a vehicle on which code P0237 is present should not be driven and especially not in traffic, because serious driveability issues can arise unexpectedly. If this happens, the vehicle can be immobilized unexpectedly, which has obvious safety risks for the vehicles’ occupants and other road users

How difficult is it to repair code P0237 ?

Merely testing and replacing the turbo charger boost pressure sensor should not present the average non-professional mechanic with undue difficulties since the sensor is and its wiring is easy to access on most applications. Note that apart from a good quality digital multimeter, a hand-held pressure pump that is fitted with a graduated gauge may be helpful in diagnosing this code if a suitable scanner is not available.

Note though that in cases where the turbo charger is damaged or not functioning correctly, special tools and equipment may be required to remove the turbo charger for inspection, testing, and replacement. In these cases, the better option is to refer the vehicle to the dealer or other competent repair facility for professional assistance.

What are the common mistakes when repairing code P0237 ?

Common mistakes when dealing with code P0237 could include the following-

  • Failure to inspect the entire inlet tract for damaged, leaking, split, and/or dislodged hoses, pipes, and clamps that can cause the loss of boost pressure
  • Failure to correct any of the above defects
  • Failure to test the actual boost pressure being developed by the turbo charger
  • Failure to recognize that even marginally defective turbo charger components can result in abnormally low boost pressures
  • Failure to inspect the air clear element, or to check the inlet tract for obstructions that can restrict air flow

How do you troubleshoot code P0237 ?

NOTE: Take note that code P0237 refers specifically to abnormally low boost pressures that are as likely to be the result of a damaged turbo charger, as it is to be result of a defective sensor or wiring. For this reason, it is imperative to inspect the turbo charger for evidence of damage, or to have the actual boost pressure tested professionally to either eliminate or confirm a damaged turbo charger as the root cause of this code. Failure to do this as the first step in the diagnostic/repair procedure could result in a misdiagnosis, wasted time, and possible damage to the engine.

Step 1

Record all fault code present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.

NOTE: If other codes are present, and especially codes that relate to the turbo charger waste gate or the waste gate control system, these codes must be resolved before an attempt is made to diagnose P0237. Failure to do this will result in a misdiagnosis, and the inability to resolve P0237.

Assuming then that no other codes are present, the entire inlet tract has been inspected for leaks or obstructions, and that the turbo charger is free of damage and in proper working order, refer to the manual to locate the boost pressure sensor and all associated wiring and connectors. Also, determine the function, and color-coding of all associated wiring to avoid a misdiagnosis later on.

Step 2

On most applications, a KOEO (key-on-engine-off) condition is required to test reference voltages, sp proceed to check the boost sensor’s reference voltage circuit, which should carry 5V, or very close to it. If no voltage is present, refer to the manual for details on the procedure to follow to check that the PCM is actually delivering a reference voltage.

WARNING: Take extreme care during this step not to cause accidental short circuits at the PCM connector that can destroy the PCM. Do NOT disconnect the PCM connector at this point, unless the manual clearly states that it must be disconnected, and only use proper back-probing adapters on the multimeter probes to test the CORRECT pin for the reference voltage. 

If the PCM is delivering the correct reference voltage, find and repair the open circuit in the reference voltage circuit. If however, the PCM does not deliver a reference voltage, replace the PCM in strict accordance with the instructions provided in the manual.

Step 3

If the reference voltage checks out, perform resistance and continuity tests on the ground and signal voltage circuits, but be sure to disconnect all relevant wiring from the PCM to avoid damaging the controller during this step.

Pay particular attention to the resistance of the signal wire. If this value does not agree with the value stated in the manual, replace the wire or make repairs as required to ensure that the circuit’s resistance falls within the range specified by the manufacturer.

Step 4

If all electrical values in the sensors’ wiring check out, test the resistance of the sensor itself, since this value is a reasonably good indicator of its overall condition. Replace the sensor if its resistance does not agree with the stated value, but only use OEM replacement parts to ensure proper operation of the replacement sensor.

If the scanner use can monitor live data streams, narrow its monitoring function down to only monitor the operation of the boost pressure sensor. Assuming all repairs are complete, start the engine and rise the engine slowly while monitoring the scanner display. On some scanners, the actual boost pressure will be displayed, while on others, only a voltage value may be displayed.

In all cases though, the displayed boost pressure value should rise smoothly as the engine speed is increased, until the maximum allowable boost pressure is attained. At this point, the displayed value should remain fairly constant; any large or erratic deviations from this value indicate either an intermittent wiring fault, or an intermittent fault in the boost pressure sensor itself.

If the scanner cannot monitor live data streams, use the multimeter to monitor the signal voltage as the engine speed is raised. However, the maximum displayed value must be compared with pressure/voltage chart in the manual to verify that maximum boost pressure is being developed at the specified engine speed.

Step 5

Clear all codes after all repairs are complete, and operate the vehicle for at least one complete drive cycle to see if the code returns. If the code does not immediately return, the repair can be considered as successful.

If however, the code does return, repeat all tests outlined above until the fault is found and repaired, but note that these types of faults can be extremely challenging and time consuming to find and repair. Thus, if an intermittent fault is suspected and steps 1 through 4 do not resolve the issue, the wisest option would be to refer the vehicle to a competent repair facility for professional diagnosis and repair.

Codes Related to P0237

  • P0235 – “Turbocharger Boost Sensor A Circuit Malfunction”
  • P0236 – “Turbocharger Boost Sensor A Circuit Range/Performance”
  • P0238 – “Turbocharger Boost Sensor A Circuit High”

 

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