Diagbox 9.129 for Beginners: Your First PSA Diagnostic Session

New to Diagbox 9.129? This beginner’s guide walks you through your first complete diagnostic session on a Peugeot, Citroën, DS, or PSA-platform Opel/Vauxhall vehicle — from connecting the interface to reading fault codes, running an actuation test, and resetting service intervals.

Before You Start

• Diagbox 9.129 VMware is installed and running (see the VMware setup guide)
• Your Lexia 3 or DiagPlug interface is plugged into your PC and passed through to the VM
• The vehicle battery is charged — low battery voltage causes false fault codes and communication errors
• All other ignition keys are removed from the vehicle during diagnostics

Step 1 — Connect to the Vehicle

1. Plug your Lexia 3 into the vehicle’s OBD2 port (usually under the dashboard, driver’s side)
2. Turn the ignition to position 2 (accessories on, engine off) — do not start the engine
3. In Diagbox, click Diagnostics from the main menu
4. Select your vehicle brand: Peugeot, Citroën, DS Automobiles, or Opel

Step 2 — Vehicle Identification

Diagbox will attempt to automatically identify the vehicle by reading the VIN from the BSI. This takes 15–30 seconds. Once identified, a screen shows:

• Vehicle model and year
• Engine type and gearbox
• All detected electronic modules

Confirm the vehicle details are correct and click Continue.

Step 3 — Full System Fault Code Scan

1. Select Fault Codes from the diagnostic menu
2. Click Read All Faults — Diagbox polls every module in the vehicle sequentially
3. Wait 60–90 seconds for the scan to complete
4. All fault codes appear grouped by system (Engine, Gearbox, ABS, Airbag, BSI, etc.)
5. Each fault shows: DTC code, description, status (present/stored), and priority level

Tip: Don’t immediately clear all faults. Read through them first — patterns across multiple systems often indicate a single root cause (e.g., multiple U-codes pointing to a CAN bus issue).

Step 4 — Reading Live Data

1. Select a system (e.g., Engine) from the module list
2. Click Parameters or Live Data
3. Start the engine
4. Select the parameters you want to monitor (coolant temp, injector pulse width, MAF airflow, etc.)
5. Diagbox displays real-time values with min/max recording

Step 5 — Running an Actuation Test

Actuation tests let you activate individual components to verify they are functioning:

1. Select the system containing the component you want to test
2. Click Actuator Tests
3. Choose the component (e.g., cooling fan, EGR valve, fuel pump)
4. Click Activate — Diagbox sends the command and you can hear/feel the component respond
5. Click Stop when done

Step 6 — Service Interval Reset

1. From the main diagnostic menu, select Maintenance or Service Functions
2. Choose Service Interval Reset
3. Select the service type (oil service, brake fluid, etc.)
4. Confirm the reset — Diagbox writes the new service date to the BSI
5. The service warning light extinguishes immediately

For common fault codes and their fixes, see our Diagbox fault codes guide. For any questions, check the Diagbox 9.129 FAQ.

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