Delco MT80.1 Immo Off: Chevrolet Aveo, Lacetti, Cruze and Opel with the MT80 ECU

The Delco (GM) MT80.1 ECU controls the 1.2, 1.4 and 1.6 petrol engines in the Chevrolet Aveo, Lacetti, Cruze, Spark (M300) and the Opel/Vauxhall versions of the same cars. It replaced the older MR140 and is common in Eastern Europe, Turkey and South America. Immobilizer faults on these cars usually trace back to the BCM or a used ECU, and the MT80.1 immo off file is the fastest fix when a new key set is out of the question.

Identify the ECU

The label shows MT80.1 or MT80 with a GM part number (25 1xx xxx or 96 xxx xxx). Different engines share the hardware but not the software, so note the full part number before ordering. The MT80.1 has an internal processor flash; there is no external chip to swap.

Immo off or pairing?

If the ECU and BCM are the car’s own units and only the keys are lost, a dealer tool (GDS2 / Tech2) can still program new keys — immo off is not necessary. Immo off makes sense when the BCM is dead, a used ECU is installed and cannot be married, or the car is exported to a market without dealer support.

Reading and writing

The MT80.1 is supported over OBD by KESS V2 (GM/Chevrolet protocol) for both read and write. If the unit does not answer, use KTAG or Flex on the bench. Reading takes under five minutes.

1. Connect a battery support unit; the write is sensitive to voltage drops.
2. Read the ECU, save the original and compare the part number and software ID with the product page.
3. Write the immo off file and let the tool finish the checksum correction.
4. Switch the ignition off for 30 seconds, then start.

After the write

The engine starts with any key that turns the lock. The security lamp on the cluster may stay lit because the BCM still reports a missing handshake; on most Aveo/Lacetti clusters it goes out after a few driving cycles. Central locking, alarm and other BCM functions are not affected.

Things that go wrong

• Wrong engine variant — a 1.4 file on a 1.6 ECU starts but idles badly. Match the GM part number.
• Voltage drop during writing — the ECU stops responding. Recover it in boot mode with KTAG and write the original.
• Code P1626/P1631 stays stored — clear it once after the flash; if it returns, the BCM is still requesting the handshake, which is harmless.

Getting the right file

Search the immo off files for Chevrolet and Opel by the GM part number on your MT80.1 label. If it is not listed, send us your original read through the file request form and we prepare the immo off version from your own file.