First post here, having spent a few months reading past threads.......
Quick synopsis of the past
Live in sunny Spain, imported the truck new from Canada
Chassis 1GBJK34163E280926
engine all stock, have a predetor for code reading mainly, until I can fix this problem.
She keeps throwing 0238 at me, took it to a so call "pro" who scanned it and he said to replace the pressure sensor....have done but to no avail..
As model not imported here officially it can be tricky to get things done but I have access to a tech 2 at a gm dealership and he says he has the sofware..

Any ideas would be a great help.

DTC P0238 (Federal RPO FE9, NG1)
Circuit Description
The boost sensor responds to pressure changes in the intake manifold. This pressure is created by the turbocharger and changes with accelerator pedal position (APP) and engine speed. The engine control module (ECM) uses this information to assist in diagnosis of the barometric pressure (BARO) sensor and to provide engine overboost protection. The boost sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The ECM supplies 5 volts to the boost sensor on a 5-volt reference circuit, and provides a ground on a low reference circuit. The boost sensor provides a voltage signal to the ECM on a signal circuit relative to the pressure changes. The ECM monitors the boost sensor signal for voltage outside of the normal range. If the ECM detects a boost sensor signal voltage that is excessively high, this DTC will set.

Conditions for Running the DTC
The ignition is ON

Conditions for Setting the DTC
The boost pressure is more than 254 kPa for 2 seconds.

Action Taken When the DTC Sets
The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
The ECM limits fuel delivery.
Conditions for Clearing the MIL/DTC
The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.
Test Description
The number below refers to the step number on the diagnostic table.

If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can aid in locating an intermittent condition.

Step
Action
Values
Yes
No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views

1
Did you perform the Diagnostic System Check-Engine Controls?
--
Go to Step 2
Go to Diagnostic System Check - Engine Controls

2
Start the engine.

Does the scan tool indicate that the boost sensor pressure is more than the specified value?
254 kPa
Go to Step 4
Go to Step 3

3
Observe the Freeze Frame/Failure Records for this DTC.
Turn OFF the ignition for 30 seconds.
Start the engine.
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.
Did the DTC fail this ignition?
--
Go to Step 4
Go to Intermittent Conditions

4
Turn OFF the ignition.
Disconnect the boost sensor electrical connector. Refer to Boost Sensor Replacement .
Turn the ignition ON, with the engine OFF.
Does the scan tool indicate that the boost sensor pressure is less than the specified value?
50 kPa
Go to Step 5
Go to Step 6

5
Turn OFF the ignition.
Connect a jumper wire between each of the terminals in the boost sensor harness connector and the corresponding terminal at the boost sensor. Refer to Using Connector Test Adapters in Wiring Systems.
Turn ON the ignition, with the engine OFF.
Measure the voltage from the low reference circuit of the boost sensor at the jumper wire terminal to a good ground with a DMM. Refer to Measuring Voltage Drop in Wiring Systems.
Is the voltage more than the specified value?
0.2 V
Go to Step 7
Go to Step 8

6
Test the signal circuit of the boost sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 12
Go to Step 9

7
Test the low reference circuit of the boost sensor for high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 12
Go to Step 9

8
Inspect for poor connections at the boost sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 12
Go to Step 10

9
Inspect for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 12
Go to Step 11

10
Replace the boost sensor. Refer to Boost Sensor Replacement .

Did you complete the replacement?
--
Go to Step 12
--

11
Replace the ECM. Refer to Engine Control Module (ECM) Replacement .

Did you complete the replacement?
--
Go to Step 12
--

12
Clear the DTCs with a scan tool.
Turn OFF the ignition for 30 seconds.
Start the engine.
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.
Did the DTC fail this ignition?
--
Go to Step 2
Go to Step 13

13
Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?
--
Go to Diagnostic Trouble Code (DTC) List
System OK

abiggs69

Many thanks I will give all this a go today will report later.

Thanks again.

If you need the schematic, pm me. I can get you those.

You have a pm

What a great place....
low ref terminal had been bent back by the blue protector case on the ecm hence bad circuit.
All ok now looking forward to the sensible mods.

Till later, bibifn

Glad you got it.