EXPERTEC TSB (91-106-6E)

Publication date: 1990-11-14
Reference number: 91-106-6E

EXPERTEC TSB

TECHNICAL SERVICE BULLETIN

Reference Number(s): 91-106-6E, Date of Issue: 11/14/90

INTERMITTENT CONNECTION AT ECM - PCM/TCM SENSORS OR COMPONENTS

Model(s): 1991 Chevrolet Light Duty Truck Models

Bulletin No.: Chevrolet 91-106-6E

Date: 11/14/1990

BULLETIN ILLUSTRATION LIST

Fig 1: Graphic

SERVICE INFORMATION

TO: ALL CHEVROLET DEALERS

Some 1991 Light duty trucks equipped with Electronic Control Modules (ECM) or Powertrain Control Modules (PCM) or Transmission Control Modules (TCM) may experience a condition, in which the female terminals (150 series METRI-pack) in certain sensor or component connectors do not make a solid connection to the male terminals in the opposing connectors. This can result in an intermittent connection. The 1991 Truck Service Manual directs a check of connections anytime an intermittent condition is found. The following chart lists the component and circuit numbers that may experience this condition.

POSSIBLE AFFECTED COMPONENTS AND CIRCUIT NUMBERS

Component	Circuit	Description
Intake Air Temperature (IAT)/ 2.5L only	472/469	IAT signal/5 volt return (ground)
Coolant Temperature Sensor (CTS)	410/452	CTS signal/5 volt return (ground)
Throttle Position Sensor (TPS)	417/452	TPS Signal/5 volt return (ground)
Electronic Spark Timing Module (EST)	453/424/430/423	EST Reference low/ESt Bypass/EST Reference high/Est control
Transmission Vehicle Speed Sensor (All Auto. & Manual Transmission)	821/822	Speed Signal high/Speed Signal low
Transmission Input Speed Sensor (4L80E only)	1230/1231	Input Speed Signal low/Input Speed Signal high
Transmission Output Speed Sensor (4L80E with Four Wheel Drive only)	1232/1233	Output Speed Sensor high/Output Speed Sensor low

If an intermittent condition is found, the following test procedure should be performed.

Insert a new mating male terminal, P/N 12047581 or 12045773, into the female terminal and check for a slight drag when the terminals are separated. Loose terminals without drag should be replaced.

If the amount of drag is questionable, remove the terminal from the connector and inspect the terminal for the condition shown in Fig 1 . Replace any terminals found defective with terminal P/N 12047680.

General directions of terminal replacement can be found in the appropriate 1991 Truck Shop Manual in the Fuel and Emissions Manual.

NOTE: Do not attempt to repair a defective terminal.

All of the above terminal part numbers are contained in J-38125 or are available from GMSPO.

Parts are currently available from GMSPO.

WARRANTY INFORMATION

For vehicles repaired under warranty use:

Labor Operation Number: T7096

Labor Time: This is a ST (Straight Time) operation which requires time documentation as detailed in the claims processing manual. Zone approval is required beyond .5 hours.

NOTE: Labor Operation is coded to base vehicle coverage in the warranty system.

Trouble Code: 92