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P1503

Theft Deterrent System Password Incorrect.

  • Oldsmobile
  • Powertrain
  • Manufacturer code
  • Medium severity

How this code is built

P
SystemPowertrain
1
Defined byThe manufacturer
5
AreaVehicle speed, idle control and auxiliary inputs
03
FaultThe specific fault in that area

What it means

On Oldsmobile, P1503 means the engine control module received an incorrect password from the theft deterrent system. The ECM and the body or immobiliser module share a coded security exchange, and when the code sent does not match what the ECM has stored, it sets this fault. The engine may be disabled or limited as a result.

Symptoms

  • Engine cranks but will not start, or starts and stalls after a second or two
  • Security or theft warning light on, flashing or staying lit
  • Intermittent no-start that comes and goes with no pattern
  • Fuel or ignition appears to be cut shortly after starting
  • Key or transponder not recognised

Possible causes

  • Faulty or poorly programmed ignition key transponder, or a worn keylikely
  • Security or immobiliser data link fault between the ECM and the body or theft module (wiring, connector or open circuit)likely
  • ECM replaced or swapped without the security password being relearnedlikely
  • Fault in the key reader or ignition lock cylinder sensorpossible
  • Low battery voltage or poor earths causing corrupted communication during crankingpossible
  • Internal fault in the ECM or the theft deterrent modulerare

How to diagnose

  1. Read all stored codes and freeze frame data, and note whether other security or communication codes are present
  2. Check battery condition and charging voltage, as low voltage can upset module communication
  3. Try a second known good, correctly programmed key to see if the fault follows the key
  4. Inspect the wiring, connectors and earths for the ECM, the body or theft module and the ignition key reader for damage, corrosion or looseness
  5. Watch the security status in live data while turning the ignition on and cranking, to see if the password exchange fails
  6. Check the security data circuit for continuity and shorts against the wiring diagram for the specific model and year
  7. Confirm whether the ECM or theft module has recently been replaced or reprogrammed, as the relearn procedure depends on model and year

How to fix

  • Replace or reprogram the ignition key transponder if the key is faulty or not learned
  • Repair damaged wiring, connectors or earths in the security data circuit
  • Carry out the security password relearn procedure after an ECM or theft module replacement, following the manufacturer procedure for that model
  • Replace a faulty key reader or ignition lock cylinder sensor
  • Correct low battery or charging problems, then clear the code and retest
  • Replace the ECM or theft deterrent module only once the wiring and key have been proven good

Can I keep driving?

Medium severity

The car may not start or may stall, so it is unreliable and could leave you stranded. If it does run, it is usable in the short term, but get it diagnosed soon before it fails to start at all.

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

This code for other makes

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