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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1327 (Automatic Transmission - Mu4 (Introduction, Service & Replacement)) >> Diagnostic Information and Procedures >> Overdrive Off Indicator Always On >> Test Description

Test Description

WARNING: This page is about a different car, the 2004 Pontiac Vibe. 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. 1:  The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
  2. 2:  This step checks for a short to ground in the O/D OFF indicator circuit.
  3. 3:  This step checks whether the condition is caused by a short to ground or a constantly closed Overdrive switch and not due to a faulty PCM.
  4. 4:  This step checks whether the condition is caused by a short to ground in the O/D OFF switch signal circuit and not due to a faulty Overdrive switch.
  5. 9:  This step checks whether the condition is caused by a short to ground in the O/D OFF switch signal circuit and not due to a faulty Overdrive switch.
Overdrive Off Indicator Always On

Step Action Yes No
Schematic Reference: Automatic Transmission Controls Schematics 
1  Was the On-Board Diagnostic (OBD) System Check performed? Go to Step 2  Go to Diagnostic System Check - Engine Controls in Engine Controls
2 
  1. Depress the Overdrive switch to the pressed position.
  2. Turn the ignition switch to LOCK.
  3. Disconnect the PCM connector C1.
  4. Turn the ignition switch to ON.
Does the O/D OFF indicator light?		 Go to Step 5  Go to Step 3 
3 
  1. Turn the ignition switch to LOCK.
  2. Connect a test lamp between B+ and the PCM harness connector C1 terminal 29.
Does the test lamp light?		 Go to Step 4  Go to Step 6 
4  With the test lamp still connected to the PCM connector, disconnect the Overdrive switch.
Does the test lamp light?		 Go to Step 8  Go to Step 7 
5 Repair the short to ground in the LT GRN wire between the PCM and the I/P cluster, or between the Overdrive switch and PCM.
Is the action complete?		 Go to Step 9  -
6 Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.
Is the action complete?		 Go to Step 9  -
7 Replace the Overdrive switch.
Is the action complete?		 Go to Step 9  -
8
  1. Depress the Overdrive switch to the pressed position.
  2. Turn the ignition switch to LOCK.
  3. Disconnect the PCM connector C3.
  4. Turn the ignition switch to ON.
Does the O/D OFF indicator light?		 Go to Step 9  -
9 
  1. Turn the ignition switch to LOCK.
  2. Reconnect all disconnected connectors.
  3. Depress the Overdrive switch.
  4. Turn the ignition switch to the ON position.
Does the O/D OFF indicator light stay off?		 System OK Go to Step 1 
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