GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Chevy P42 Commercial Chassis 🢒 DTC 🢒 DTC 37 TCC Brake Switch Low Input

Object Number: 230152 Size: MF
Automatic Transmission Components Gasoline
Handling ESD Sensitive Parts Notice

Circuit Description

The TCC Stoplamp switch indicates the brake pedal status. The normally-closed TCC Stoplamp switch supplies a B+ signal on circuit 420 to the Transmission Control Module (TCM). The signal voltage circuit opens when the brakes are applied. The TCM uses the open signal voltage circuit in order to de-energize the Torque Converter Clutch Pulse Width Modulation Solenoid Valve (TCC PWM Sol. Valve) when the brakes are applied.

If the TCM detects an open TCC Stoplamp switch circuit during accelerations, then DTC 37 sets.

Conditions for Setting the DTC
    • The following sequence of events occurs seven consecutive times:
       - The vehicle speed is less than 8 km/h (5 mph) for 6 seconds.
       - Then vehicle speed is 8 40 km/h (5 25 mph) for 6 seconds.
       - Then the vehicle speed is greater than 40 km/h (25 mph) for 6 seconds.
    • The TCM detects an open TCC Stoplamp switch/circuit (0 volts).

Action Taken When the DTC Sets
    • The TCM does not illuminate the Malfunction Indicator Lamp (MIL).
    • The TCM inhibits TCC.
    • The TCM inhibits 4th gear if in hot mode.
    • DTC 37 is stored in TCM history.

Conditions for Clearing the DTC
    • The TCM clears the DTC from Current to History when the fault condition(s) no longer exist and the ignition switch is cycled OFF and then ON.
    • A scan tool can clear the DTC from Current and History status. The TCM clears the DTC from the TCM history if the vehicle completes 40 ignition cycles without a failure reported.
    • The TCM cancels the DTC default actions when the fault no longer exists and the ignition is cycled OFF and then ON.

Diagnostic Aids
    • Inspect the wiring at the TCM, the TCC Stoplamp Switch and all other circuit connecting points for the following conditions:
       - A bent terminal
       - A backed out terminal
       - A damaged terminal
       - Poor terminal tension
       - A chafed wire
       - A broken wire inside the insulation
       - Moisture intrusion
       - Corrosion
    • When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
    • Ask about the customer's driving habits and any unusual driving conditions he or she might have, such as stop and go traffic or expressway driving.
    • Inspect the brake switch for proper mounting and adjustment.
    • Inspect for the most current calibration ID and the latest bulletins.

Test Description

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

  1. This step tests for TCC Stoplamp switch voltage to the TCM connector.

  2. This step isolates the TCC Stoplamp switch as a source for setting the DTC.

    3.

  3. This step tests for a short to ground in circuit 241 (ignition voltage) to the TCC Stoplamp switch.

    4.

  4. This step tests for a short to ground in circuit 420, from the TCC Stoplamp switch to the TCM.

    5.

  5. This step isolates the TCM as a source for causing the fuse to open.

DTC 37

Step

Action

Value(s)

Yes

No

1

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to On-Board Diagnostic System Check

2
  1. Install the Scan Tool .
  2. With the engine OFF, turn the ignition switch to the RUN position.

    3. Important:: Before clearing the DTC's, record the Current and History DTC's information for reference. The Clear Info function erases the stored Current and History DTC from the TCM.

  3. Record Current and History DTC's, then clear the DTC.
  4. Select the TCC Brake Switch on the Scan Tool .
  5. Do not apply the brake pedal.

Does the Scan Tool TCC Brake switch indicate CLOSED, when the brake pedal is not applied?

--

Go to Diagnostic Aids

Go to Step 3

3
  1. Remove the 1-3 (#9) fuse.
  2. Inspect the 1-3 fuse for an open.

Refer to General Electrical Diagnosis .

Is the fuse open?

--

Go to Step 10

Go to Step 4

4

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the C 2 (24 pin) connector from the TCM. Additional DTC's may set.
  3. Connect a 12 volt test lamp to a good ground.
  4. Using the J 35616-A Connector Test Adaptor Kit and the 12 volt test lamp connected to ground, probe terminal C 2 - B 4 (420 PPL).
  5. Re-install the fuse.
  6. Turn the ignition switch to the RUN position.
  7. Do not apply the brake pedal.

Is the test lamp on?

--

Go to Step 15

Go to Step 5

5
  1. Turn the ignition key to the OFF position.
  2. Remove the connector from the TCC Stoplamp switch.
  3. Use the J 39200 DMM to measure B + voltage at terminal A (241 BRN) of the TCC Stoplamp switch connector.
  4. Turn the ignition switch to the RUN position.

Is B + voltage indicated?

10 - 13 volts

Go to Step 7

Go to Step 6

6

Inspect circuit 241 for an open. Refer to General Electrical Diagnosis .

Did you find and correct an open condition?

--

Go to Step 17

--

7

  1. Turn the key to the RUN position.
  2. Install a fused jumper wire from terminal B (420 PPL) to terminal A (241 BRN) of the TCC Stoplamp switch connector.
  3. Probe the TCM connector terminal C 2 - B 4 (420 PPL) with the test lamp.

Is the test lamp on?

--

Go to Step 9

Go to Step 8

8

Inspect circuit 420 for an open. Refer to General Electrical Diagnosis .

Did you find and correct an open condition?

--

Go to Step 17

--

9

Replace the TCC/Stoplamp Switch. Refer to Stop Lamp Switch Replacement .

Is the replacement complete?

--

Go to Step 17

--

10

  1. Turn the key to the RUN position.
  2. Apply and hold the brake pedal.
  3. Install a new fuse while keeping the brake pedal applied.

Does the fuse open with the brake pedal applied?

--

Go to Step 11

Go to Step 12

11

Inspect circuit 241 for a short to ground. Refer to General Electrical Diagnosis .

Did you find and correct the short to ground condition?

--

Go to Step 17

--

12

With the key in the RUN position, release the brake pedal.

Does the fuse open when the brake pedal is released?

--

Go to Step 13

Go to Diagnostic Aids

13

  1. Turn the key to the OFF position.
  2. Disconnect the C 2 (24PIN) connector from the TCM (additional DTC's may set).
  3. Turn the key to the RUN position.
  4. Install a new fuse.
  5. Do not apply the brake pedal.

Does the fuse open?

--

Go to Step 14

Go to Step 15

14

Inspect circuit 420 (PPL) for a short to ground. Refer to General Electrical Diagnosis .

Did you find and correct the short to ground condition?

--

Go to Step 17

--

15

Inspect the TCM terminals for shorted, corroded or weak connections.

Did you find a condition?

--

Go to Step 17

Go to Step 16

16

Replace the TCM. Refer to DTC 51 PROM Error TCM Replacement.

Is the replacement complete?

--

Go to Step 17

--

17

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

  1. Select DTC.
  2. Select Clear Info.
  3. Operate the vehicle under the following conditions:
    4. 3.1. With the engine OFF, turn the ignition switch to RUN position.
    3.2. The brake pedal is not applied.
    3.3. Select TCC Brake Switch on the Scan Tool .
    3.4. Observe the Scan Tool TCC Brake Switch status.
    3.5. Apply the brake pedal.

Does the TCC Brake Switch indicate Closed when the brake pedal is not applied, then indicate Open when the brake pedal is applied?

--

Repair verified, exit DTC table

Begin Diagnosis again

Go to Step 1