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TPS Adjustment (Diesel)

  1. Loosen Throttle Position Sensor (TPS) retaining screws. If TPS is being replaced, install new TPS on injection pump and lightly tighten screws. Make jumper wires using the following General Motors' parts: Terminals No. 1214836 and 12014837. Install jumper wires between TPS and harness.
  2. Turn ignition on, but DO NOT  start engine. Install .646" (16.41 mm) thick Gauge Block (J-33043-2) between gauge boss on injection pump and wide open throttle valve stop screw on throttle lever (switch on position).
  3. Rotate throttle shaft and hold the wide open throttle stop screw against gauge block. Using a DVOM, measure reference voltage across terminals "A" (Black wire) and "C" (Gray wire). Record voltage reading. Now measure and record TPS return voltage between terminals "B" (Dark Blue wire) and "C" (Gray wire).
  4. Divide TPS return voltage by the reference voltage. For example: a TPS return voltage of 3.15 volts divided by a 5.01 reference voltage equals a .63 TPS voltage ratio. Refer to the TPS ADJUSTMENT SPECIFICATIONS  table. The TPS voltage ratio uncertainty should be within ±.03 volts.
  5. To adjust TPS, loosen attaching screws and rotate TPS until a correct TPS voltage ratio is obtained. Tighten attaching screws to 53 INCH lbs. (6 N.m).
  6. Release throttle lever and allow it to return to the idle stop position. Check TPS voltage between terminals "B" (Dark Blue wire) and "C" (Gray wire). Now return lever against gauge block and note voltage reading.
  7. Voltage should be less than 2.2 volts at closed throttle and return to within ±.03 volts of the adjusted voltage when throttle is against gauge block.
  8. If reading does not return to adjusted voltage, repeat adjustment procedure. If reading is still incorrect or if voltage is not less than 2.2 volts with throttle closed, replace TPS.
  9. After TPS adjustment, remove gauge block. Turn ignition off. Remove jumper wires and reconnect TPS harness connector. Install air cleaner assembly and related hoses.
TPS ADJUSTMENT SPECIFICATIONS

Application TPS Voltage Ratio
Automatic Transmission .63
Manual Transmission .63
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