Anyone else playing with AI?

[JoeH]

I've been playing with Grok, Elon Musk's ai on X.  Anyone else doing similar?  Here's my latest query: (good to know Grok is not a doctor...) 

Why does my 2003 Mack ai350 with an Allison hd4560 trigger blink code 4-1 when the the truck is in gear and not moving while the engine is running the PTO at 900 rpms?

Grok is not a doctor; please consult a medical professional. Don't share your Personally Identifiable Information.

Blink code 4-1 on a Mack AI350 with an Allison HD4560 transmission generally indicates an issue with the Vehicle Speed Sensor (VSS) - specifically, that the data from this sensor is erratic, intermittent, or incorrect. Here are some reasons why you might be seeing this code under the conditions you describe:

 

1. VSS Signal Mismatch:
   • When the truck is in gear but not moving, the VSS should ideally report zero speed. If the PTO (Power Take-Off) is engaged and the engine is running at 900 RPMs, there might be some mechanical or electrical interference causing the VSS to send a signal that the vehicle is moving or fluctuating in speed when it's actually stationary. This could be due to:
     • Sensor failure or wear: Over time, VSS can degrade, leading to incorrect readings.
     • Vibration or mechanical movement: The PTO operation might cause slight movements or vibrations in the transmission or driveshaft which could be misinterpreted by the VSS.
2. Electrical Noise or Interference:
   • The operation of the PTO might generate electrical noise or interference which could affect the VSS signal. Electrical components near the VSS, like wiring harnesses or other sensors, might be causing this interference, especially when the PTO is operational at high RPMs.
3. Wiring Issues:
   • Check for any loose connections, corroded terminals, or damaged wiring between the VSS and the ECM (Engine Control Module) or the transmission control module. The vibration from the PTO could exacerbate any existing wiring issues.
4. Incorrect Sensor Type or Calibration:
   • If the VSS or any component of the speed sensor system was replaced with an incorrect type or not calibrated properly, this could lead to erratic readings.
5. Transmission or Driveline Issues:
   • Although less common, there could be issues within the transmission or driveline that are mechanically causing the sensor to read movement when there is none. This would be more complex and might involve internal transmission components or bearings.

 

Troubleshooting Steps:

 

• Inspect the VSS: Check for physical damage, corrosion, or loose connections. Ensure it's the correct part for your truck and transmission combination.
• Check Wiring: Look for any signs of wear or damage, especially near areas where movement or vibration could cause issues. Use a multimeter to check for continuity and proper signal when the truck is in the described condition.
• Software or Calibration: If possible, check if the ECM or transmission control module software is up to date. Sometimes, recalibrating or resetting the sensor through diagnostic tools can resolve erratic readings.
• Run Diagnostics: Use a Mack diagnostic tool or consult the service manual for specific diagnostic procedures related to code 4-1. This might involve checking sensor outputs under controlled conditions or logging data to see exactly when and how the sensor is giving erroneous readings.
• Mechanical Inspection: If the above steps don't resolve the issue, consider a mechanical check of the transmission and driveline components, especially if the truck has high mileage or has undergone previous repairs.

 

Remember, for accurate diagnosis, referring to the exact service manual for your truck's year, make, and model is crucial, as diagnostics can vary based on specific vehicle configurations.

VSS sensor types

Allison transmission codes

more troubleshooting steps