Miata Technical Service Bulletin

Section Applicable Model(s) Subject
Bulletin No. 001/99
Issued 03/04/99
T (01) 1999 Miata Fluctuation in Cruise Control Set Speed

Applicable Model(s)/VINS

All 1999 Miatas with VINs lower than JM1NB35** X0 122015


During the auto cruise control function, any of the following problems may occur:

These symptoms may be caused by a transistor malfunction inside the cruise control unit. A modified part with a heavy duty transistor is available to resolve this concern.

Cutomers complaining of this concern should have their vehicle repaired using the following procedure.

Repair Procedure

  1. Verify customer complaint.
  2. Measure the battery voltage and note it on the repair order.
  3. Turn the ignition switch ON, then turn the cruise control main switch ON.
  4. Measure voltage of cruise control module at terminal 'A' (G/Y wire). Refer to Section 01-20 of the Workshop Manual.
  5. Verify repair.

Parts Information

Part Number Description Qty. Notes
NC12 66 320 Cruise Control Unit 1 -

Warranty Information


Warranty Type Code: A
Symptom Code: 54
Damage Code: 9W
Part No. Of Main Cause NC12 66 320
Quantity: 1
Operation No./ Labor Hour: T0804XRX / 0.5

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