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P1504

Vehicle Speed Output Circuit.

  • Chrysler
  • Powertrain
  • Manufacturer code
  • Low severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
5
AreaVehicle speed, idle control and auxiliary inputs
04
FaultThe specific fault in that area

What it means

P1504 on a Chrysler is logged against the Vehicle Speed Output Circuit. The engine control unit produces a vehicle speed signal for other systems and checks the output circuit. It set the code because the signal it commanded did not match what it saw on the circuit, which points to an open circuit, a short or a driver fault. Which systems use this signal varies by model and year, so check the wiring information for the vehicle.

Symptoms

  • Check engine light on
  • Speedometer or odometer erratic or not working, on models where the signal feeds the cluster
  • Cruise control not working or dropping out
  • Other systems that use the speed signal behaving oddly, such as speed-sensitive features
  • No obvious driveability problem in some cases

Possible causes

  • Damaged wiring or poor connector contact in the vehicle speed output circuit (open circuit, chafing, corrosion or short to ground or voltage)likely
  • Fault in a module that receives the speed signal, loading or pulling down the circuitpossible
  • Faulty input from the vehicle speed or wheel speed source that the output signal is generated frompossible
  • Poor power or earth supply to the engine control unit affecting its output driverpossible
  • Internal fault in the engine control unit output driverrare
  • Outdated control unit software where a technical bulletin covers this code for the modelrare

How to diagnose

  1. Read all stored and pending codes and the freeze frame data, and note any speed sensor or communication codes that point to a related fault.
  2. Check whether the speedometer, cruise control and other speed-dependent systems work, and note which fail, as this narrows down the circuit.
  3. Look up the wiring diagram for the exact model and year to find where the speed output goes and which modules use it.
  4. Inspect the wiring and connectors on that circuit for chafing, water ingress, corrosion, pushed-out pins and previous repairs.
  5. With the connectors disconnected, test the circuit for continuity, short to ground and short to voltage against the wiring diagram.
  6. Check the engine control unit power and earth supplies, including fuses and earth points.
  7. Monitor the live vehicle speed data on a road test to confirm the input source is plausible and steady.
  8. Check for any applicable software update or technical bulletin for the model before considering the control unit faulty.

How to fix

  • Repair or replace damaged wiring and clean or replace corroded or loose connectors on the speed output circuit.
  • Replace any receiving module that is found to be pulling the circuit down, after confirming it is faulty.
  • Repair the vehicle speed or wheel speed input fault if that is the source of the signal.
  • Restore good power and earth connections to the engine control unit.
  • Replace or repair the engine control unit only if the output driver is confirmed faulty, and update its software if a bulletin applies.

Can I keep driving?

Low severity

The car can normally be driven, but book it in soon. A faulty speedometer or cruise control may make driving less safe or lawful, and it can fail an MOT if the speedometer is affected.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

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