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HOMESERVICE MANUALSCHEVROLET2006CHEVY EXPRESS G2500, VAN CARGO, 6.6 2REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 962 (ENGINE CONTROL SYSTEM & FUEL SYSTEM - 4.3L - DTC P0507 TO DTC P2A04)DTC P1121TEST DESCRIPTION
2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2

Test Description

2006 Chevrolet Chevy Express G2500, Van Cargo, 6.6 2SECTION Test Description
WARNING: This page is about a different car, the 2007 GMC Savana and 2007 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.

The number below refers to the step number on the diagnostic table.

  1. 7:  This test will determine an intermittent faulty TP sensor utilizing the MIN MAX, 100-millisecond capture mode on the DMM.
DTC P1121

Step Action Yes No
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views
1 Did you perform the Diagnostic System Check - Vehicle? Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Disconnect the throttle position (TP) sensor electrical connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Measure the voltage from the 5-volt reference circuit of the TP sensor to a good ground with a DMM.
  4. Lightly touch and move the related engine wiring harnesses and connectors for all 5-volt reference circuits while observing voltage. Any change in voltage indicates the area where a short to voltage may be found. Refer to Testing for Electrical Intermittents and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 9  Go to Step 3 
3
  1. Measure the voltage from the signal circuit of the TP sensor to a good ground with a DMM.
  2. Lightly touch and move the related engine wiring harnesses and connectors while observing voltage. Any change in voltage indicates the area where a short to voltage may be found. Refer to Testing for Electrical Intermittents and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 9  Go to Step 4 
4
  1. Measure the resistance from the low reference circuit of the TP sensor to a good ground with a DMM.
  2. Lightly touch and move the related engine wiring harnesses and connectors while observing resistance. Any change in resistance indicates the area where an open or high resistance may be found. Refer to the following:
Did you find and correct the condition?		 Go to Step 9  Go to Step 5 
5 Test for intermittent and for poor connections at the TP sensor harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 9  Go to Step 6 
6 Test for intermittent and for poor connections at the powertrain control module (PCM) harness connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 9  Go to Step 7 
7 
  1. Turn OFF the ignition.
  2. Measure the resistance between the TP sensor signal terminal and the low reference terminal at the TP sensor using the MIN MAX function on the DMM.
  3. Slowly press the accelerator pedal to the wide open throttle (WOT) position, then release the pedal back to the closed throttle position several times.
Did you observe a MAX value of infinite ohms or a MIN value of 0 ohms.		 Go to Step 8  Go to Testing for Intermittent Conditions and Poor Connections
8 Replace the TP sensor. Refer to Throttle Position Sensor Replacement .
Did you complete the replacement?		 Go to Step 9  -
9
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.
Did the DTC fail this ignition?		 Go to Step 2  Go to Step 10 
10 Observe the Capture Info with a scan tool.
Are there any DTCs that have not been diagnosed?		 Go to Diagnostic Trouble Code (DTC) List - Vehicle System OK
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.