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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Optra 🢒 Transmission/Transaxle 🢒 Automatic Transmission - ZF 4HP 16 🢒 DTC P1606

DTC P1606 Non-Europe or N. American Emissions

Circuit Description

In case the transmission control module (TCM) reset has occurred by software (warm reset) and not by ignition key ON, the TCM increments software resets the counter. If the counter exceeds the permissible maximum value for the software count, then the fault will be detected.

Conditions for Setting the DTC
    • System voltage is too high or too low.
    • Transaxle input voltage is too high or too low.
    • Immediately after the above condition occurs

Action Taken When the DTC Sets
    • The hold lamp will blink.
    • The TCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffer.
    • Adopt Emergency/Substitute mode and constant 4th gear.
    • Power supply cut off to the pressure control solenoid (PCS) valve.

Conditions for Clearing the Hold Lamp/DTC
    • The hold lamp will turn OFF when the malfunction has not occurred after 3 ignition cycles.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • Using a scan tool can clear history DTCs.

DTC 1606

Step

Action

Values

Yes

No

1

Perform the Diagnostic System Check.

Is the check complete?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2
  1. Install the scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. Record then clear the DTCs.
  4. Turn the ignition OFF, then turn the ignition ON and start the engine.
  5. Run the engine to 1,200 RPM.
  6. Select system voltage on the scan tool.
  7. Drive the vehicle. Observe the scan tool for system voltage.

Is the voltage within the specified value?

9-16 V

Go to Step 4

Go to Step 3

3
  1. Disconnect the negative battery cable.
  2. Measure the voltage of the battery at the battery.

Is the voltage within the specified value?

9-16 V

Go to Step 4

Go to Diagnostic System Check - Engine Electrical in Engine Electrical

4
  1. Turn the headlamp ON.
  2. Turn the air conditioner ON.
  3. Run the engine to 1,200 RPM.
  4. Observe the scan tool for system voltage.

Is the voltage within the specified value?

9-16 V

Go to Step 6

Go to Step 5

5
  1. Turn the ignition OFF.
  2. After testing the charging system, repair the alternator circuit if necessary.

Is the action completed?

--

System OK

--

6

The vehicle will not start if F2 or EF1 were defective.

Was a problem found?

--

Go to Step 7

Go to Step 8

7

Replace the fuse, if necessary.

Is the replacement complete?

--

System OK

--

8
  1. Turn the ignition ON, with the engine OFF.
  2. Measure the voltage of F2, EF1.

Is the voltage within the specified value?

9-16 V

Go to Step 10

Go to Step 9

9

Repair the fuse voltage supply lines for an open.

Is the action completed?

--

System OK

--

10
  1. Turn the ignition OFF.
  2. Disconnect the transmission control module (TCM) wiring connector.
  3. Measure the resistance between EF1 fuse and terminal  B3 of the TCM wiring connector.

Is the resistance approximately equal to the specified value?

0 ohms

Go to Step 12

Go to Step 11

11

Repair the circuit between EF1 and terminal B3 for short to ground and open.

Is the repair completed?

--

System OK

--

12
  1. Disconnect the C105 connector and the TCM connector.
  2. Turn the ignition ON, with the engine OFF.
  3. Measure the voltage of the terminal B3, the TCM wiring connector.

Is the voltage within the specified value?

9-16 V

Go to Step 13

Go to Step 14

13

Repair the circuit from EF1 to terminal B3 of the TCM for a short to power.

Is the repair complete?

--

System OK

--

14
  1. Turn the ignition OFF.
  2. Disconnect the C206 connector.
  3. Measure the resistance between F2 fuse and terminal C15 or C16 of the TCM wiring connector.

Is the resistance approximately equal to the specified value?

0 ohms

Go to Step 16

Go to Step 15

15

Repair the circuit between F2 and terminal C15 or C16 for a short to ground and open.

Is the repair completed?

--

System OK

--

16
  1. Turn the ignition ON, with the engine OFF.
  2. Measure the voltage of the terminal C15 or C16, the TCM wiring connector.

Is the voltage within the specified value?

9-16 V

Go to Step 17

Go to Step 18

17

Repair the circuit between F2 and terminal C15 or C16 for short to power.

--

System OK

--

18
  1. Inspect the transaxle wiring for poor electrical connections at the transaxle connector.
  2. Look for possible bent, backed out, deformed, or damaged terminals.
  3. Inspect for weak terminal tension.

Was a condition found?

--

Go to Step 20

Go to Step 19

19

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the replacement complete?

--

Go to Step 20

--

20
  1. After the repair, use a scan tool "clear info" function.
  2. Road test the vehicle.
  3. Review the DTC info.

Has the last test failed or is the current DTC displayed?

--

Go to Step 2

System OK

DTC P1606 European and N. American Emissions

Circuit Description

The external watchdog will be triggered. If the external watchdog does not run out after 30 ms then the fault will be detected.

Conditions for Setting the DTC
    • System voltage is too high or too low.
    • Transaxle input voltage is too high or too low.
    • Immediately after the above condition occurs

Action Taken When the DTC Sets
    • The malfunction indicator lamp (MIL) will illuminate.
    • The transmission control module (TCM) will record operating conditions at the time the diagnostic fails. This information will be stored in the Failure Records buffer.
    • Adopt Emergency/Substitute mode and constant 4th gear by hydraulic control.
    • After ignition OFF/ON : 3rd gear by hydraulic control. Possible P, R and N also possible.
    • Power supply cut off to the pressure control solenoid (PCS) valve.

Conditions for Clearing the MIL/DTC
    • The MIL will turn OFF when the malfunction has not occurred after 3 ignition cycles.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • Using a scan tool can clear history DTCs.

Diagnostic Aids

When DTC P1606 sets, the possible cause of fault could be the TCM.

DTC 1606

Step

Action

Yes

No

1

Perform the Diagnostic System Check.

Is the check complete?

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission

2
  1. Install the scan tool.
  2. Turn the ignition ON, with the engine OFF.

Does the scan tool display P1606?

Go to Step 3

Go to Diagnostic Aids

3

Inspect EF1 or F2 fuse for open.

Was a problem found?

Go to Step 4

Go to Step 5

4

Replace the fuse as necessary.

Is the action completed?

System OK

--

5
  1. Turn the ignition OFF.
  2. Disconnect the transmission control module (TCM) wiring connector.
  3. Inspect the wiring harness for short to battery between the fuses EF1 or F2 and the TCM terminals B3, C15, or C16.

Was a problem found?

Go to Step 10

Go to Step 6

6

Inspect the wiring harness for open between the fuses EF1 or F2 and the TCM terminals B3, C15 or C16.

Was a problem found?

Go to Step 10

Go to Step 7

7

Inspect the wiring harness for open or short to ground between TCM terminals B12 or B13 and G201.

Was a problem found?

Go to Step 10

Go to Step 8

8

Inspect the wiring harness for short to power between the terminals B12 or B13 and G201.

Was a problem found?

Go to Step 10

Go to Step 9

9

Replace the TCM. Refer to Transmission Control Module Replacement .

Is the replacement complete?

Go to Step 10

--

10
  1. Using the scan tool, clear the DTCs.
  2. Road test the vehicle within the Conditions for Setting this DTC, as specified in the text.

Does the scan tool indicate that this diagnostic has run and passed?

Go to Step 11

Go to Step 2

11

Inspect if any DTCs are set.

Are any DTCs displayed that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List/Type

System OK