Note On Intermittents

Manipulate related PCM and BCM wiring in each gear range while looking for a change in ED31 or BD41 display values to check for intermittent open or short to ground. Also check terminals for good contact at PCM, BCM and PRND  D21 switch. If good contact exists and Code B127 continues to set, replace PRND  D21 switch.

Fig 1: Code B127 - Troubleshooting Diagram 1 of 3 (Toronado & Trofeo)

Courtesy of GENERAL MOTORS CORP.

1. Checks for short to ground in gear selector switch to BCM circuits.
2. Checks for open in circuits to BCM.
3. Circuit shorted to ground will result in a "0" for that circuit.
4. Checks for open PRND  D21 sensor ground.
5. Circuit with open will result in a "1" for that circuit.
   Fig 2: Code B127 - Troubleshooting Diagram 2 of 3 (Toronado & Trofeo)

   Courtesy of GENERAL MOTORS CORP.
6. The snap data value of DB41 display will be the value that BCM recognized when code was set. This is used to determine whether this value is valid. If it is a valid, PCM park/neutral input must be incorrect to set code.

Fig 3: Code B127 - Troubleshooting Diagram 3 of 3 (Toronado & Trofeo)

Courtesy of GENERAL MOTORS CORP.