LEMON Manuals: Even more car manuals for everyone
Home >> GMC >> 2005 >> Sierra 1500 HD, 4WD >> Repair and Diagnosis >> External Pages >> Different car >> Section 213 (Automatic Transmission - 5L40-E/5L50-E - (DTC P0757 To DTC P1833)) >> DTC P1820 >> Test Description

Test Description

WARNING: This page is about a different car, the 2005 Cadillac STS. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 3:  This step determines if the fault is internal or external to the transmission.
  2. 4:  This step determines if the engine wiring harness circuit or the TCM is at fault.
  3. 5:  This step determines if the automatic transmission wiring harness or the IMS is at fault.
DTC P1820

Step Action Value(s) Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
    3. IMPORTANT:
    • Before clearing the DTC, use the scan tool in order to record the ECM Freeze Frame and the TCM Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the ECM and the TCM.
    • Using the Clear Info function erases stored DTCs in both the ECM and TCM.
  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Select Transmission Data on the scan tool.
  6. Select IMS range on the scan tool.
  7. Place the gear select lever in D.
Does the scan tool IMS range display Drive?		 - Go to Intermittent Conditions in Engine Controls - 3.6L or Intermittent Conditions in Engine Controls - 4.6L Go to Step 3 
3 
  1. Turn OFF the ignition.
  2. Disconnect the AT inline 20-way connector. Additional DTCs may set.
  3. Turn ON the ignition, with the engine OFF.
  4. Select IMS A/B/C/P on the scan tool.
Does the scan tool IMS Signal A display LOW?		 - Go to Step 4  Go to Step 5 
4  Test the TR signal A circuit of the switch for a short to ground between the TCM connector and the AT inline 20-way connector.
Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 - Go to Step 9  Go to Step 8 
5 
  1. Turn OFF the ignition.
  2. Connect the AT inline 20-way connector.
  3. Disconnect the automatic transmission wiring harness at the transmission manual shift shaft switch assembly.
  4. Turn ON the ignition, with the engine OFF.
  5. Select IMS A/B/C/P on the scan tool.
Is the IMS Signal A displaying LOW?		 - Go to Step 6  Go to Step 7 
6 Replace the automatic transmission internal wiring harness. Refer to Transmission Internal Electrical Harness Replacement .
Is the action complete?		 - Go to Step 9  -
7 Replace the transmission manual shift shaft switch assembly. Refer to Manual Shaft Shift Position Switch Replacement .
Is the action complete?		 - Go to Step 9  -
8 Replace the TCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.
Is the action complete?		 - Go to Step 9  -
9 Perform the following procedure in order to verify the repair:
  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    • Drive the vehicle in D4.
    • IMS Signal A must be HI for 0.025 second.
  4. Select Specific DTC.
  5. Enter DTC P1820.

Has the test run and passed?		 - Go to Step 10  Go to Step 2 
10 With the scan tool, observe the stored information, capture info and DTC info.
Does the scan tool display any DTCs that you have not diagnosed?		 - Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information System OK
scientia non olet · About LEMON Manuals