Scania ATA DTC 121 Glow plug

ATA ATA control unit · Scania

Code 121 (decimal). Some diagnostic tools show it in hexadecimal as 0079.

In short

The auxiliary heater does not start.

Applies to: ATA1ATA2

What does Scania ATA fault code 121 mean?

The auxiliary heater does not start.

What causes Scania DTC 121?

Open circuit in the glow plug circuit.

How does the system react?

Important! 18 V glow plug! The glow plug must not be connected directly to + 24 V.

How to fix Scania ATA fault code 121?

  1. Check the glow plug.
  2. See the Internal electrical diagram under Connections.
  3. Measurement points 1 and 2 in harness-to-harness connector B for the control unit.
  4. Resistance: - 2 +/- 0.2 ohms.
  5. If necessary, renew the control unit.

This information is for guidance only. Always follow the manufacturer workshop manual and safety procedures; if in doubt, contact an authorised workshop.

Code 121 in other Scania systems

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