Diagnostic Scan

Perform a complete diagnostic scan of all vehicle control modules to retrieve fault codes and system status information for troubleshooting purposes.

Warnings

Tools required

Preparation

1. Park vehicle on level ground and set parking brake
2. Turn off all electrical accessories including radio, HVAC, and lights
3. Ensure battery voltage is at least 12.4V - connect battery charger if needed to maintain voltage during scan
4. Gather vehicle service history and note any recent repairs or symptoms
5. Allow engine to cool if performing scan after driving to prevent heat-related sensor readings from confusing diagnosis

Procedure

1. 1

   Locate and access OBD-II diagnostic port
   The OBD-II diagnostic port is located under the dashboard on the driver's side, just to the left of the steering column. It may have a protective cover that pulls off. Ensure the port is clean and free of debris or damage to pins.
2. 2

   Connect scan tool and turn ignition on
   Plug the scan tool firmly into the OBD-II port until it clicks into place. Turn the ignition key to the ON/RUN position without starting the engine. The scan tool should power up and establish communication. If using a wireless adapter, wait for the connection indicator to confirm pairing.
3. 3

   Initialize scan tool and select vehicle
   Follow scan tool prompts to select 2007 Dodge Ram 3500 with 5.9L Cummins diesel engine. Some scan tools will auto-detect the vehicle via VIN. Verify the correct vehicle and engine are selected before proceeding to ensure accurate module identification and code definitions.
4. 4

   Scan Engine Control Module (ECM)
   Navigate to Engine/Powertrain module and perform a complete scan. Record all Diagnostic Trouble Codes (DTCs) — note that the 5.9L Cummins ECM reports faults via SAE J1939 as SPN/FMI codes in addition to any generic OBD-II P-codes — along with their freeze frame data, and code status (pending, current, or stored). Note engine runtime data, coolant temperature, and any active warnings. The 5.9L Cummins ECM is the primary diagnostic module and may contain critical powertrain fault information.
5. 5

   Scan Transmission Control Module (TCM)
   Access the Transmission Control Module and retrieve all stored and active codes. For automatic transmissions, check transmission temperature, gear position, and shift adaptations. Record any U-codes (network communication codes) that may indicate module communication issues. Note if vehicle has manual or automatic transmission as this affects available data.
6. 6

   Scan Anti-lock Brake System (ABS) module
   Navigate to ABS/Brake module and retrieve all C-codes (chassis codes). Check wheel speed sensor data to verify all four sensors are reading correctly and similarly when vehicle is stationary. Record any stored codes related to wheel speed sensors, hydraulic pump/motor, or ABS control solenoid valve operation.
7. 7

   Scan Airbag/Supplemental Restraint System (SRS)
   Access the SRS/Airbag module and retrieve all B-codes (body codes). Note any crash data stored in memory and airbag deployment history. Check status of all airbag sensors, seat belt pretensioners, and occupant detection systems. Document any impact sensor faults or communication errors.
8. 8

   Scan Body Control Module (BCM) and other modules
   Access the Body Control Module to check for lighting, door lock, and accessory-related codes. Scan any additional available modules including: instrument cluster, HVAC control, and transfer case control (4WD system). Note that the 5.9L Cummins is not equipped with a diesel particulate filter (DPF) system — that emissions component was introduced with the later 6.7L Cummins. Record all codes and note which modules are present and communicating.
9. 9

   Review live data and system parameters
   Navigate to live data stream for the Engine Control Module. Monitor key parameters including: fuel rail pressure (target vs actual), turbo boost pressure (MAP sensor), coolant temperature, intake air temperature, accelerator pedal position (APPS), and manifold absolute pressure readings. Note that this diesel does not use a throttle plate or MAF sensor. Compare readings to known good specifications and note any values that appear out of range or illogical.
10. 10

    Check readiness monitors and emissions status
    Access the OBD-II readiness monitors section. Check status of all emissions-related monitors (catalyst monitor may not apply to diesel, but others will). Note if any monitors show 'Not Ready' status which may indicate recent code clearing or incomplete drive cycles. This is important for emissions testing compliance.
11. 11

    Document all findings and save report
    Save or print complete scan report including all DTCs, freeze frame data, and module information. Record VIN, current mileage, and date of scan. If scan tool has save/export function, save data for future reference. Create written documentation of all codes with descriptions, noting which are current faults versus historical stored codes.
12. 12

    Clear codes if appropriate and verify
    Only clear codes if diagnosis is complete and repairs are planned, or if specifically testing for intermittent issues. After clearing, perform a re-scan to verify codes were cleared and check if any immediately return. If codes return immediately, this indicates an active fault condition requiring immediate attention.

Reassembly

1. Disconnect scan tool from OBD-II port and reinstall protective cover if equipped
2. Turn ignition off and remove key
3. Disconnect battery charger if one was used during the procedure

Verification

• Review all recorded diagnostic trouble codes and correlate with customer complaint or symptoms
• Cross-reference any DTCs with factory service manual for proper diagnosis and repair procedures
• Verify all vehicle control modules communicated successfully - lack of communication may indicate module failure or wiring issues
• Check that readiness monitors are appropriate for vehicle condition and recent service history
• If codes were cleared, perform a short test drive and re-scan to verify no codes return immediately
• Compare live data readings to factory specifications to identify sensors or systems operating outside normal parameters

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