Cruise Control - Set Speed Fluctuation

Bulletin No. 001/99
Issued 03/04/99
Revised

Section
T (01)

Applicable Model/s
1999 Miata

Subject
FLUCTUATION IN CRUISE CONTROL
SET SPEED

APPLICABLE MODEL(S)/VINS

All 1999 Miata with VINs lower than JM1 NB35** X0122015.

DESCRIPTION

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

^ Vehicle speed fluctuation

^ Cruising speed is 5-7 m.p.h. higher than the set speed

^ Coast function (deceleration system) becomes inoperative

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.

Customers 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.

^ If voltage at terminal "A" is at least 1 .0V lower than the battery voltage measured in Step 2, replace cruise control module with modified part.

^ If voltage difference between battery and terminal 'A' is within 1.0 V, cruise control unit has no problem.

5. Verify repair.

PART(S) INFORMATION

Part Number Description Qty. Notes

NC12 66 320 Cruise Control Unit 1 --

WARRANTY INFORMATION

Note
This information applies to verified customer complaints on vehicles covered under normal warranty. Refer to the SRT microfiche for warranty term information.

Warranty Type A

Symptom Code 54

Damage Code 9W

Part Number Main Cause NC12 66 320

Quantity 1

Operation Number / Labor Hours T0804XRX / 0.5