[NickD]

Just curious as to whom did you purchase this vehicle from? Private party, are screwed, used car dealer, a fight, new car dealer, responsible for only selling unmodified vehicles that meet strict EPA requirements. Most states have lemon laws that even apply to used vehicles.

Being on the frugal side, fell off my chair after I got on the gmpartsdirect.com site to learn what the exhaust system cost from the manifold back, last thing in the world I would want to cut up. For years and going way back, replacing the exhaust system with this dam road salt was a yearly job. Was very pleased with our 04 Cavalier, made it passed ten years before problems occurred. Our now defunct Cruze, no thanks to a drunk was hitting the five year mark, exhaust was still in very good shape.

So is it the pressure sensor or with unauthorized modifications is your cat toast? This can be tested if you know how.

 

[NickD]

Turbo air temperature and pressure tested is mounted on top of the inlet hose to the turbo.

Here is the procedure for testing it.

"
DTC P0236

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure See: Testing and Inspection\Initial Inspection and Diagnostic Overview.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach See: Testing and Inspection\Initial Inspection and Diagnostic Overview.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category See: Testing and Inspection\Initial Inspection and Diagnostic Overview.

DTC Descriptor

DTC P0236
Turbocharger Boost Sensor Performance

Circuit Description

The boost pressure sensor is integrated with the turbocharger boost/intake air temperature sensor. The boost pressure sensor measures the range of pressures between the turbocharger and the throttle body. The sensor used on this engine is a three atmosphere sensor. Pressure in this portion of the induction system is affected by engine speed, throttle opening, turbocharger boost pressure, Intake air temperature (IAT), barometric pressure (BARO), and the efficiency of the charge air cooler.

The sensor provides a signal voltage to the engine control module (ECM), relative to the pressure changes. Under normal operation the greatest pressure that can exist in this portion of the induction system at ignition ON, engine OFF is equal to the BARO. When the engine is operated at wide-open throttle (WOT) the turbocharger can increase the pressure to near 240 kPa (34.8 psi). The pressure is equal to the BARO when the engine is idling or decelerating.

Conditions for Running the DTC

• DTC P0096, P0097, P0098, P0102, P0103, P0107, P0108, P0111, P0112, P0113, P0116, P0117, P0118, P0119, P0128, P0237, P0238, P0335, P0336, P2227, P2228, P2229, or P2230 is not active.
• Engine speed is between 400-7,000 RPM.
• Engine Coolant Temperature (ECT) is between -7 to +125°C (19.4-257°F).
• Intake Air Temperature (IAT) is between -20 to +125°C (-4 to +257°F).
• The DTC runs continuously when the above conditions have been met.

OR

• DTC P0106, P0107, P0108, P0237, P0238, P2227, P2228, P2229, P2230, or P2610 s not active.
• DTC P0107, P0108, P0237, P0238, P2228, or P2229 is not pending.
• Ignition is ON.
• Engine is OFF
• The time between current ignition cycle and the last time the engine was running is greater than 6 s.
• The DTC runs continuously when the above conditions have been met.

Conditions for Setting the DTC

• The ECM detects that various combinations of Turbocharger Intake Flow Rationality Diagnostic Failure models, derived from engine speed, the BARO sensor, the MAF sensor, the MAP sensor, the throttle position sensor and the turbocharger boost pressure sensor have failed when the engine is running.

OR

• The ECM detects that the boost pressure sensor signal is less than 50 kPa (7.3 psi) or greater than 115 kPa (16.7 psi) when the ignition is ON and the engine is NOT rotating.

Action Taken When the DTC Sets

• DTC P0236 is a Type B DTC.
• The ECM will disable boost control and limit the system to mechanical boost only, resulting in a substantial decrease in engine power.

Conditions for Clearing the MIL/DTC

DTC P0236 is a Type B DTC.

Diagnostic Aids

• The charge air cooler is connected to the turbocharger and to the throttle body by flexible duct work that requires the use of special high torque fastening clamps. These clamps cannot be substituted. In order to prevent any type of air leak when servicing the duct work, the tightening specifications and proper positioning of the clamps is critical, and must be strictly adhered to.
• Use a smoke generating device or a solution of dish soap and water in a spray bottle to pinpoint any suspected air leaks in the induction system and in the charge air cooler assembly.

Reference Information

Schematic Reference
Engine Controls Schematics See: Powertrain Management\Diagrams\Electrical

Connector End View Reference
Component Connector End Views See: Diagrams\Connector Views

Description and Operation
Turbocharger System Description See: Powertrain Management\Fuel Delivery and Air Induction\Turbocharger\Description and Operation

Electrical Information Reference

• Circuit Testing See: Testing and Inspection\Component Tests and General Diagnostics
• Connector Repairs See: Testing and Inspection\Component Tests and General Diagnostics
• Testing for Intermittent Conditions and Poor Connections See: Testing and Inspection\Component Tests and General Diagnostics
• Wiring Repairs See: Testing and Inspection\Component Tests and General Diagnostics

DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions See: Diagnostic Trouble Code Descriptions

Scan Tool Reference
Control Module References for scan tool information See: Testing and Inspection\Programming and Relearning

Circuit/System Verification

1. Verify that DTC P0641 is not set.

=>	If the DTC is set

Refer to DTC P0641, P0651, P0697, or P06A3.

• If the DTC is not set

1. If you were sent here from DTC P0068, P0101, P0106, P0121, or P1101, refer to Circuit/System Testing.
2. Ignition ON.
3. Verify the scan tool Throttle Body Idle Airflow Compensation parameter is less than 90%.

=>	90% or greater

Refer to Throttle Body Inspection and Cleaning.

• If less than 90%

1. Verify the scan tool Throttle Position Sensors 1 and 2 Agree/Disagree parameter displays Agree while performing the Throttle Sweep Test with a scan tool.

=>	If Disagree

Refer to DTC P0121-P0123, P0222, P0223, or P2135.

• If Agree

1. Verify the scan tool BARO parameter is within the range specified in the Altitude Versus Barometric Pressure table, for the current vehicle testing altitude.

=>	BARO is not in range

Refer to DTC P2227-P2230.

• BARO is within range

1. Verify the scan tool MAP Sensor pressure and BARO parameters are within 3 kPa (0.4 psi) .

=>	The parameters are not within 3 kPa (0.4 psi).

Refer to DTC P0106.

• The parameters are within 3 kPa (0.4 psi).

1. Engine idling.
2. Verify the scan tool MAP Sensor pressure parameter is between 26-52 kPa (3.8-7.5 psi) and changes with accelerator pedal input.

=>	If not between 26-52 kPa (3.8-7.5 psi) or does not change.

Refer to DTC P0106.

• If between 26-52 kPa (3.8-7.5 psi) and changes

1. Verify the scan tool MAF Sensor g/s parameter changes smoothly and gradually as the engine speed is increased and decreased while performing the actions listed below.

10.1.	Engine idling
10.2.	Perform the scan tool snapshot function.
10.3.	Increase the engine speed slowly to 3,000 RPM and then back to idle.
10.4.	Exit from the scan tool snapshot and review the data.
10.5.	Observe the MAF Sensor parameter frame by frame with a scan tool.
=>	The MAF Sensor parameter does not change smoothly and gradually.

Refer to DTC P0101.

• The MAF Sensor parameter changes smoothly and gradually

1. Verify the scan tool Boost Pressure Sensor pressure and BARO parameters are within 3 kPa (0.4 psi) .

=>	The parameters are not within 3 kPa (0.4 psi).

Refer to Circuit/System Testing

• The parameters are within 3 kPa (0.4 psi).

1. Verify the scan tool MAP Sensor parameter and the Boost Pressure Sensor parameter are within 20 kPa (2.9 psi) during a WOT acceleration at the time of the 1-2 shift.

=>	The parameters are not within 20 kPa (2.9 psi)

Refer to Circuit/System Testing.

• The parameters are within 20 kPa (2.9 psi)

1. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
2. Verify a DTC does not set.

=>	If a DTC sets

Refer to Circuit/System Testing.

• If a DTC does not set

1. All OK.

Circuit/System Testing

1. Verify that DTC P0237 or P0238 is not set.

=>	If a DTC is set

Refer to DTC P0237 or P0238.

• If none of the DTCs are set

1. Verify the conditions listed below do not exist:

• • Loose clamps, cracks, or other damage in the air intake duct system
  • Collapsed or restricted air intake duct system
  • Restricted air filter
  • Splits, kinks or improper connections at the vacuum hoses
  • Missing, restricted or leaking exhaust components - Refer to Symptoms - Engine Exhaust.
  • Vacuum leaks at the intake manifold and throttle body

=>	If a condition exists

Repair as necessary.

• If none of the conditions exist

1. Replace the B111B turbocharger boost/intake air temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

• Intake Air Pressure and Temperature Sensor Replacement for turbocharger boost/intake air temperature sensor replacement See: Powertrain Management\Computers and Control Systems\Air Temperature Sensor ( Ambient / Intake )\Service and Repair.
• Control Module References for engine control module replacement, programming, and setup See: Testing and Inspection\Programming and Relearning."

Have fun