DTC P1812 Transmission Fluid Overtemperature. Chevrolet Brazil Blazer 1997

For 1990-2009 cars
Automatic Transmission Components 4.3L
Automatic Transmission Controls Schematics 4.3L
OBD II Symbol Description Notice

### Circuit Description

The flow of transmission fluid starts in the bottom pan and is drawn through the filter, control valve body assembly, transmission case and into the oil pump assembly. The oil pump assembly pressurizes the fluid and directs it to the pressure regulator valve where it becomes the main supply of fluid to the various components and hydraulic circuits in the transmission. Hot fluid exiting the torque converter flows through the converter clutch apply valve and into the transmission cooler lines to the oil cooler located in the vehicle radiator (and auxiliary cooler if equipped). From the cooler, fluid returns to cool and lubricate the front of the transmission. In forward drive ranges, D4 fluid from the manual valve is routed through an orificed cup plug in the rear of the transmission case to feed the rear lube fluid circuit.

When the VCM detects a high transmission temperature for a long period of time, then DTC P1812 sets. DTC P1812 is a type D DTC.

### Conditions for Setting the DTC

• | No TFT sensor DTCs P0712 or P0713.

• | The TFT is greater than 136°C (277°F).

• | All conditions met for 410 seconds (6.8 minutes).

### Action Taken When the DTC Sets

• | The VCM freezes shift adapts from being updated.

• | The VCM does not illuminate the Malfunction Indicator Lamp (MIL).

### Conditions for Clearing the DTC

• | A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.

• | The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

### Diagnostic Aids

• | The TFT sensor temperature displayed on the scan tool should rise steadily to a normal operating temperature, then stabilize.

• | Ask about the customer's driving habits, trailer towing, etc. Trailer towing should occur in D3.

### Test Description

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

1. This step checks for air flow restrictions or damage which may result in the transmission overheating.

#### DTC P1812 Transmission Fluid Overtemperature

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to A Powertrain On Board Diagnostic (OBD) System Check

2

1. Install the scan tool (tech 1) ®.
2. With the engine OFF, turn the ignition switch to the RUN position.

Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the VCM.

3. Record the DTC Failure Records, then clear the DTC(s).
4. Perform the transmission fluid checking procedure. Refer to 4L60-E Transmission Fluid Checking Procedure.

Was the fluid checking procedure performed?

--

Go to Step 3

Go to Transmission Fluid Check

3

1. Inspect the engine cooling system and transmission cooling system for the following conditions:

• | Air flow restrictions

• | Air flow blockage

• | Debris

2. Inspect the transmission cooling system for damaged cooler lines.

Was a problem found?

--

Go to Step 6

Go to Step 4

4 | Perform the line check procedure. Refer to 4L60-E Line Pressure Check . Was a problem found? | -- | Go to Step 6 | Go to Step 5
5 | Inspect the torque converter stator for damage. Refer to Torque Converter Clutch (TCC) Diagnosis . Was a problem found? | -- | Go to Step 6 | Go to Diagnostic Aids

6

In order to verify your repair, perform the following procedure:

1. Select DTC.
2. Select Clear Info.
3. Ensure that the following conditions are met:

• | With the engine OFF, the ignition switch is in the RUN position.

• | The scan tool indicates a TFT less than 130°C (266°F) for at least 5 seconds.

4. Select Specific DTC. Enter DTC P1812.

Has the test run and passed?

--

System OK

Begin the diagnosis again. Go to Step 1