Code 87, Shift Solenoid "B" Stuck "Off" - LT. Truck: Notes

The shift solenoids are used inside the valve body to control spool valve position, which determines the transmission gear.

Fused ignition power is supplied to solenoid "B". The PCM/TCM will engage solenoid "B" by grounding circuit No. 1223 to energize the solenoid. See Figure.

Code 37 will set under the following conditions:

• Vehicle speed is greater than 7 MPH.
• TPS is more than 25 percent.
• PCM/TCM commands 3rd or 4th gear.
• Transmission ratio indicates transmission is in 1st or 2nd gear.
• Conditions are met for 6 seconds.
  NOTE: Test numbers refer to test numbers on diagnostic chart.
  1. This test checks PCM/TCM's ability to ground or control solenoid "B". If bidirectional Scan tester is not available, solenoid may be activated by grounding ALDL test terminal -E with ignition on and engine off.
  2. This test checks the power supply and circuit No. 1223.
  3. This test checks the internal transmission harness and solenoid "B".