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Test Description

WARNING: This page is about a different car, the 2007 Cadillac DTS. 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 is at fault or the TCM.
  3. 5:  This step determines if the automatic transmission wiring harness is at fault or the IMS.
DTC P1823

Step Action Values Yes No
1 Did you perform the Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
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 Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the TCM.
  3. Record the DTC Freeze Frame and Failure Records.
  4. Clear the DTC.
  5. Select IMS on the scan tool.
  6. Place the gear select lever in D4.
Does the scan tool IMS display Drive 4?		 - Go to Testing for Intermittent Conditions and Poor Connections 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.
Is signal P LOW?		 - Go to Step 4  Go to Step 5 
4  Test the signal P circuit of the IMS 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 .
Did you find and correct the condition?		 - Go to Step 9  Go to Step 8 
5 
  1. Turn OFF the ignition.
  2. Reconnect the AT inline 20-way connector.
  3. Disconnect the automatic transmission wiring harness at the IMS.
  4. Turn ON the ignition, with the engine OFF.
  5. Select IMS A/B/C/P on the scan tool.
Is signal P LOW?		 - Go to Step 6  Go to Step 7 
6
IMPORTANT: The automatic transmission wiring harness consists of 2 separate harnesses, the Automatic Transmission Wiring Harness Assembly and the Automatic Transmission Wiring Extension Harness Assembly. In order to avoid the unnecessary replacement of parts, determine which harness contains the fault and replace only that harness.
Replace the automatic transmission wiring harness.Refer to Input Speed Sensor and Wiring Harness Removal .Did you complete the replacement?		 - Go to Step 9  -
7 Replace the transmission internal mode switch.
Refer to Lower Control Valve Body Assembly Disassemble .
Did you complete the replacement?		 - Go to Step 9  -
8 Replace the TCM.
Refer to Control Module References .
Did you complete the replacement?		 - 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.
    • The engine torque is 50-1492 N.m (37-1100 lb ft).
    • IMS signal P must be HI, ignition voltage input, for 4 seconds.
  4. Select Specific DTC.
  5. Enter DTC P1823.

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 System OK
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