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DTC codes / Mercedes-Benz codes / P1630

P1630 · Mercedes-BenzDrive Authorization Signal

P1630 on Mercedes-Benz vehicles indicates that the drive authorization system (DAS) has detected an invalid or missing signal from the electronic ignition switch (EIS) to the engine control module (ECM). The ECM expects a coded authorization signal before allowing the engine to start, and when that signal is absent or corrupted, the ECM stores this fault and typically prevents starter operation or fuel delivery.

SystemPowertrain
Code typeMercedes-Benz specific
SeverityHigh
Fix difficultyProfessional
AreaComputer and output circuits

Symptoms you may notice

  • Engine cranks but does not start, or starter does not engage at all
  • No symptoms besides the warning light in some cases, especially if the fault is intermittent
  • Intermittent no-start condition that may resolve after cycling the key or waiting
  • Key may not be recognized, and the central locking or immobilizer indicator may behave erratically
  • Dashboard may show 'Start Error' or a key symbol, and other control modules may log communication faults

Common causes, most likely first

  1. Faulty electronic ignition switch (EIS) not sending the drive authorization signal
  2. Defective key or transponder coil in the ignition switch
  3. Corroded or damaged wiring between the EIS and the engine control module
  4. Engine control module (ECM) internal fault preventing it from reading the authorization signal
  5. Low battery voltage or poor ground connection causing intermittent communication
  6. Aftermarket alarm or remote start system interfering with the immobilizer circuit

How to diagnose and fix it

  1. Check battery voltage and condition, and load-test the battery if it is more than three years old
  2. Inspect and clean the key transponder coil and ignition switch area for corrosion or debris
  3. Scan all modules for stored codes, especially in the EIS and ECM, and record freeze-frame data
  4. Perform a drive authorization system test with a Mercedes-Benz-specific scan tool to verify signal status
  5. Check wiring continuity and resistance between the EIS and ECM connectors, looking for chafed or corroded pins
  6. Try a known-good key or reprogram the existing key to the EIS if the scan tool supports it
  7. Replace the electronic ignition switch (EIS) and perform coding if all other checks pass

Before you replace the ignition switch

  • A weak battery is the most common cause of intermittent P1630 on Mercedes-Benz models, so always load-test the battery before condemning the EIS or ECM.
  • Aftermarket alarm systems or remote starters spliced into the immobilizer wiring frequently disrupt the drive authorization signal and set this code.
  • P1630 can be stored as a history code without any current no-start symptom, so clear it and verify whether it returns before replacing parts.
  • Corrosion at the EIS connector or a loose ground strap near the engine bay can mimic a failed ignition switch and cause this code.
  • Some Mercedes-Benz models require the EIS and ECM to be matched with a dealer-level scan tool after replacement, so a used EIS will not simply plug and play.

Can I keep driving with P1630?

Do not drive the vehicle if it will not start or if the engine stalls immediately after starting, because the drive authorization system is preventing normal operation. If the car starts and runs but the warning light is on, have it diagnosed promptly, as the fault may leave you stranded without warning.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for Mercedes-Benz vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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