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Tim's Auto Repair
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Experience:  Have owned a repair shop for 25 yrs.
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2003 suburban: ltr..what engine code p1516 is please and thanks

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5.3 ltr 2003 suburban.need to know what engine code p1516 is please and thanks. badnews


this code is for the accelerator pedal sensor

Service and Repair


NOTE: Refer to Handling Electronic Throttle Control Notice in Cautions and Notices.


  1. Remove the left Instrument Panel (IP) lower closeout insulator panel.



  1. Disconnect the electrical connector from the accelerator pedal sensor module.
  2. Remove the accelerator pedal.



  1. Install the accelerator pedal to the steering column support bracket. NOTE: Refer to the Fastener Notice in Cautions and Notices. IMPORTANT: Always use a torque wrench in order to obtain the proper torque.
  2. Install the accelerator pedal mounting bolts. Tighten Tighten the accelerator pedal mounting bolts to 20 N.m (15 lb ft) .



  1. Connect the electrical connector to the accelerator pedal sensor module.
  2. Test for proper throttle opening and closing range by operating the accelerator pedal and monitoring the throttle angles using a scan tool. The accelerator pedal should operate freely without binding between full closed throttle and Wide Open Throttle (WOT) .
  3. Inspect the carpet fit under the accelerator pedal.
  4. Install the left IP lower closeout insulator panel.

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Diagnostic Chart (Part 1 Of 3)
Diagnostic Chart (Part 2 Of 3)
Diagnostic Chart (Part 3 Of 3)
Refer to Engine Controls Schematics for complete circuit details.

The commanded throttle position, based on accelerator pedal position and possibly other limiting factors, is compared to the actual throttle position. The 2 values should be within a calibrated range of each other. Both the Powertrain Control Module (PCM) and the Throttle Actuator Control (TAC) module redundantly monitor the Commanded and Actual throttle position. This Diagnostic Trouble Code (DTC) sets if the TAC module detects the problem.



  • DTC P1518 is not set.
  • The ignition switch is in the crank or run position.
  • The ignition voltage is more than 5.23 volts .
  • Not in battery saver mode


  • The TAC module detects that the commanded and actual throttle positions are not within a calibrated range of each other or the PCM and the TAC cannot determine throttle position or both TP sensors are invalid.
  • All of the above conditions are met for less than 1 second .


  • The PCM will illuminate the Malfunction Indicator Lamp (MIL) when this diagnostic runs and fails.
  • The Reduced Engine Power message displays on the drivers information center.
  • The PCM records the operating conditions at the time during which the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.
  • If no other TAC system DTCs are set, the TAC system will operate in Reduced Engine Power mode. If certain TAC system DTCs are set at the same time, the TAC system either defaults to a more tightly restricted mode of operation if the TAC determines that limited safe operation is possible, or the TAC commands the engine to shut down.


  • The PCM turns OFF the MIL after three consecutive drive trips during which the diagnostic runs and does not fail.
  • A last test failed Current DTC will clear when the diagnostic runs and does not fail.
  • A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures.
  • Use a scan tool in order to clear the MIL/DTC information.



  • Remove any debris from the PCM or TAC module connector surfaces before servicing the PCM or TAC module. Inspect the PCM or TAC module connector gaskets when diagnosing or replacing the modules. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion into the PCM or TAC modules.
  • For any test that requires probing the PCM or a component harness connector, use the J 35616-A connector test adapter kit. Using this kit prevents damage to the harness/component terminals. Refer to Using Connector Test Adapters in Diagrams.
  • The following problems may cause an intermittent:
  • Poor connections - Refer to Testing for Intermittent and Poor Connections in Diagrams.
  • Corrosion
  • A mis-routed harness
  • A rubbed-through wire insulation
  • A broken wire inside of the insulation
  • Inspect the TAC module connectors for signs of water intrusion. When this occurs, multiple DTCs should be set and no circuit or component problems can be located.
  • Ensure that the starting and charging systems are operating properly. Low system voltage causes this DTC to set.
  • When the TAC module detects a problem within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual problem may correct more than one DTC. keep this in mind when reviewing captured DTC info.
  • For an intermittent condition,

The numbers below refer to the step numbers on the diagnostic table.

  1. If the TP indicated angle does not follow the movement of the throttle blade, and no TP sensor DTCs are set, there is a mechanical condition with the throttle shaft or the TP sensor. Re-install the air inlet duct after you complete the repairs.
  1. When a condition is detected within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. It is possible that locating and repairing one individual condition may correct more than one DTC. Keep this in mind when reviewing captured DTC info.


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