Code
P1615
OLDSMOBILE
P — Powertrain
Loss Of VTD Serial Data
Views:
UK: 33
EN: 59
RU: 37
AI status
Completed
Completed
100%
Causes
- Faulty VTD module
- Open, shorted or damaged serial-data wiring (connectors, chafing, corrosion)
- Poor power or ground to the VTD module (blown fuse, bad ground)
- Other module on serial bus not responding or holding the bus low
- Aftermarket alarm/immobilizer interference or improper installation
- Intermittent connections (moisture, corrosion)
Symptoms
- Security/theft warning lamp illuminated or flashing
- Remote keyless entry or immobilizer functions inoperative or intermittent
- Vehicle may fail to arm/disarm security system; some vehicles may not crank
- Other modules report communication errors or related DTCs
- Stored communication DTCs and possible reduced functionality of body systems
What to check
- Scan vehicle and record all stored DTCs and freeze frame data; note time/date and recurrence
- Visually inspect VTD module connectors for corrosion, bent pins, or water intrusion
- Check related fuses and measure battery voltage—ensure good battery and charging system
- With key ON, verify VTD module is present on the network using a scan tool (module list)
- Backprobe power and ground pins at VTD connector to confirm proper voltages and grounds
- Inspect serial data wiring harness for damage, pinched sections, or recent repairs/aftermarket devices
Signal parameters
- Serial data is a digital bi-level signal — should show activity (pulses) when key is ON or when modules communicate
- On GM-style Class 2/serial buses the line will toggle between near 0 V and near battery voltage; no toggling indicates no activity or bus held low/high
- A healthy network will show periodic traffic and module-specific responses to diagnostic requests
- Intermittent or noisy signals may appear as erratic voltage transitions or missing message frames
Diagnostic algorithm
- Retrieve and log all DTCs (including U-codes) and clear then attempt to re-create the fault.
- Verify battery voltage is within specification. Low battery can cause communication faults.
- Inspect VTD connector and wiring for physical damage, corrosion or disconnected pins; repair as needed.
- Check fuses and relay(s) that supply the VTD module; verify power and ground at the module with a DVOM.
- Use a scan tool to see if the VTD module is detected on the network. If the module is not present, check upstream wiring and connectors.
- Probe the serial data line at the VTD connector with a scope or data logger. Confirm there is serial activity when the key is ON and that the line is not shorted to ground/battery.
- Wiggle test harness while observing data and module presence to find intermittent faults.
- Isolate and repair any shorted/open wiring or poor grounds. Remove aftermarket alarm/remote modules for testing if installed.
- If wiring and power/ground are good and the module does not appear on the bus or respond to diagnostics, consider replacing the VTD module per manufacturer procedures.
- After repairs, clear codes, verify proper communication, and perform a test drive or operation cycles to confirm repair.
Likely causes
- Disconnected or corroded connector at VTD module
- Blown fuse or missing power/ground to VTD module
- Damaged or shorted serial data wiring between VTD and main bus
- Faulty VTD module
- Aftermarket alarm/remote start interfering with serial communications
Fault status
Status
VTD module not communicating on vehicle serial data network. Causes include loss of power/ground, damaged serial-data wiring, or failed VTD module. May disable theft deterrent functions.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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