P0608: Control Module VSS Output 'A' Malfunction
The P0608 code indicates that the powertrain control module (PCM) has detected a malfunction in the vehicle speed sensor (VSS) output circuit 'A'. This circuit provides a speed signal to other modules, such as the transmission control module or instrument cluster. The PCM monitors the VSS output and if the signal is missing, erratic, or out of range, it sets this code. Common causes include a faulty VSS, wiring issues, or a defective PCM.
01. Most Common Causes
- Faulty vehicle speed sensor (VSS)
- Damaged or corroded wiring/connectors in the VSS circuit
- Defective powertrain control module (PCM)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Speedometer inoperative or erratic
- Transmission shifting issues (harsh or delayed shifts)
- Cruise control inoperative
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to verify the code and check for other related codes.
Step 2: Inspect the VSS and its wiring for damage, corrosion, or loose connections.
Step 3: Test the VSS output signal with a multimeter or oscilloscope while rotating the drive wheels.
Step 4: If the sensor and wiring are okay, test the PCM's VSS input/output circuits per manufacturer procedures.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances because the transmission may shift improperly, potentially causing damage. The vehicle may also lose speedometer and cruise control functions.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for a DIY replacement of the VSS. If professional diagnosis and repair are needed, including PCM replacement, costs can exceed $500.