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A/T - Early TCC Engagement

Model Year 1983

Bulletin No. 83-32A

File in Group 70

Number 1A

Date May '83
SUBJECT: Early TCC Engagement - All Vehicles Using An ECM Controlled TCC

NOTICE: This Bulletin supersedes Bulletin 83-32, File Group 70, Number 1, dated Dec. 1982, to include updated information. Please discard original Bulletin and replace with new Bulletin 83-32A.


Buicks exhibiting an early TCC engagement causing a stumbling or detonating condition may be due to grease or dirt on the two (2) reflective bars of the speedometer head that serve as reflective panels for the VSS signal. Any foreign material on these bars will interfere with their reflective properties, thereby generating a false (higher) vehicle speed signal to the ECM.

Dealers equipped with an ALCL tool can quickly check this by comparing speedometer reading to MPH reading the ECM is receiving. If the reading on the ALCL tool is much higher than the speedometer reading, this is usually a good indication that the reflective surfaces have foreign material interfering with their reflective properties.

The reflective bars should be thoroughly cleaned if this condition is found.

All other normal diagnostic procedures should be followed before suspecting this condition.