STOP AND START SYSTEM, Diagnostic DTC:P1538

DTC Code	DTC Name
P1538	Circuit Malfunction between AT Oil Pump and Stop and Start ECU

DESCRIPTION

The oil pump of the automatic transaxle assembly stops operating when the engine is stopped by stop and start control. While the engine is stopped by stop and start control, the oil pump with motor assembly is operated continuously ensuring optimal automatic transaxle oil pressure and smooth start-off when the engine is restarted.

The engine stop and start ECU supplies power to the oil pump assembly via terminal OP21 and operates the oil pump with motor assembly in accordance with signals sent from terminal OPM1. The oil pump with motor assembly sends operating speed signals to the engine stop and start ECU via the NOPM signal line.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Warning Indicate	Memory
P1538	Circuit Malfunction between AT Oil Pump and Stop and Start ECU	Both of the following conditions are met for 2 seconds or more (1 trip detection logic): Oil pump motor relay circuit in the engine stop and start ECU is off Oil pump with motor assembly power supply malfunction (Oil pump motor relay circuit in the engine stop and start ECU stuck on or shorted) or a short to ground in the NOPM circuit1 Both of the following conditions are met for 1 second or more (2 trip detection logic): Engine started Oil pump with motor assembly circuit malfunction (Oil pump motor relay in the engine stop and start ECU stuck off, open or short to ground in the OP21, OPM1 or NOPM circuit or an open in the GND circuit)2	Wire harness or connector Oil pump with motor assembly (Automatic transaxle assembly) Engine stop and start ECU	Blinks	DTC stored

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Warning Indicate

Memory

P1538

Circuit Malfunction between AT Oil Pump and Stop and Start ECU

Both of the following conditions are met for 2 seconds or more (1 trip detection logic):

Oil pump motor relay circuit in the engine stop and start ECU is off
Oil pump with motor assembly power supply malfunction (Oil pump motor relay circuit in the engine stop and start ECU stuck on or shorted) or a short to ground in the NOPM circuit*1

Both of the following conditions are met for 1 second or more (2 trip detection logic):

Engine started
Oil pump with motor assembly circuit malfunction (Oil pump motor relay in the engine stop and start ECU stuck off, open or short to ground in the OP21, OPM1 or NOPM circuit or an open in the GND circuit)*2

Wire harness or connector
Oil pump with motor assembly (Automatic transaxle assembly)
Engine stop and start ECU

Blinks

DTC stored

*1: "Abnormal" is displayed for the freeze frame data item [Status of O/P Signal 1]

*2: "Abnormal" is displayed for the freeze frame data item [Status of O/P Signal 2]

CONFIRMATION DRIVING PATTERN

Tech Tips

DTCs for the stop and start system are not cleared even if the malfunction has been repaired. After repairing the malfunction, be sure to clear the DTCs.

Click here

CONFIRMATION AFTER TROUBLESHOOTING
Tech Tips
- If the cable is disconnected from the battery terminal, stop and start control is prohibited until refresh charge is completed.
  
  In this case, let the vehicle idle to complete the refresh charge. The refresh charge is complete when the Data List item [Status of Battery Charge Control] changes from "Refresh Charge Mode". (Usually, idling the engine for 5 to 60 minutes with the battery fluid temperature at 11°C (52°F) or higher, the refresh charge will be completed.)
- If the GTS is not available and the Data List item [Status of Battery Charge Control] cannot be checked, charge the battery by idling the engine for approximately 5 to 60 minutes or driving the vehicle, and then drive the vehicle and check that stop and start control operates.
  
  If the engine is started with the hood open, the system determines that a jump start has occurred. Therefore, make sure that the hood is closed before starting the engine and driving the vehicle.
- After the refresh charge completes, turn the engine switch off, wait for at least 30 seconds, and then start the engine again. If the vehicle enters refresh charge mode again while the engine is idling, the initial refresh charge did not properly complete, so wait for the refresh charge to complete.
- Allow the engine to idle for 3 minutes after it is warmed up and check that the engine idle speed is within 50 rpm of the target idle speed.
1. Connect the GTS to the DLC3.
2. Turn the engine switch on (IG) and turn the GTS on.
3. Clear the DTCs.
4. Start the engine and warm it up.
5. Drive the vehicle at 7 km/h (4.3 mph) or more.
  
  CAUTION:
  
  When performing Confirmation Driving Pattern, obey all speed limits and traffic laws.
6. Depress the brake pedal and stop the vehicle.
7. Keep the engine stopped by stop and start control. (Keep the shift lever in D.)
8. Release the brake pedal with the shift lever in D to start the engine.
9. Check that no DTCs are output.
STOP AND START SYSTEM OPERATION CHECK
Tech Tips
- If the cable is disconnected from the battery terminal, stop and start control is prohibited until refresh charge is completed.
  
  In this case, let the vehicle idle to complete the refresh charge. The refresh charge is complete when the Data List item [Status of Battery Charge Control] changes from "Refresh Charge Mode". (Usually, idling the engine for 5 to 60 minutes with the battery fluid temperature at 11°C (52°F) or higher, the refresh charge will be completed.)
- If the GTS is not available and the Data List item [Status of Battery Charge Control] cannot be checked, charge the battery by idling the engine for approximately 5 to 60 minutes or driving the vehicle, and then drive the vehicle and check that stop and start control operates.
  
  If the engine is started with the hood open, the system determines that a jump start has occurred. Therefore, make sure that the hood is closed before starting the engine and driving the vehicle.
- After the refresh charge completes, turn the engine switch off, wait for at least 30 seconds, and then start the engine again. If the vehicle enters refresh charge mode again while the engine is idling, the initial refresh charge did not properly complete, so wait for the refresh charge to complete.
1. Start the engine and warm it up.
2. Turn the air conditioning system off.
3. Drive the vehicle at 7 km/h (4.3 mph) or more.
  
  CAUTION:
  
  When performing Confirmation Driving Pattern, obey all speed limits and traffic laws.
4. Depress the brake pedal and stop the vehicle.
5. Allow the engine to stop by stop and start control. (Keep the shift lever in D.)
6. Release the brake pedal with the shift lever in D to start the engine.

WIRING DIAGRAM


*a	NOPM
*b	Oil Pump with Motor Assembly (Automatic Transaxle Assembly)
*c	Engine Stop and Start ECU

CAUTION / NOTICE / HINT

Note

Before replacing the engine stop and start ECU, read the number of starter operations and write it into a new engine stop and start ECU.

Click here
After replacing the engine stop and start ECU or air conditioning amplifier assembly, reset and perform learning of the air conditioning information in the engine stop and start ECU.

Click here
After replacing the engine stop and start ECU, airbag sensor assembly*1 or yaw rate and acceleration sensor*2, clear and calibrate the deceleration sensor zero point in the engine stop and start ECU.

Click here

*1: for Optitron Meter Type
*2: for TFT Meter Type

Bleed the oil pumpy with motor assembly (automatic transaxle assembly) after removing and installing the automatic transaxle assembly or replacing the automatic transaxle fluid.

Click here

Tech Tips

Using the GTS, read the freeze frame data before troubleshooting. System condition information is recorded as freeze frame data the moment a DTC is stored. This information can be useful when troubleshooting.

Click here

PROCEDURE

CHECK FREEZE FRAME DATA

Note

The freeze frame data is cleared when DTCs are cleared. Be sure to make a note of necessary data in advance.

According to the display on the GTS, select DTC P1538 and check the sets of freeze frame data.

Click here

Result

Tester Display	Result	Proceed to
Status of O/P Signal 1	Abnormal	A
Status of O/P Signal 2	Abnormal	B

PERFORM ACTIVE TEST USING GTS (AT OIL PUMP (LO)) Click here

CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - OIL PUMP WITH MOTOR ASSEMBLY)

Disconnect the A65 and A66 engine stop and start ECU connectors.
Disconnect the D68 oil pump with motor assembly (automatic transaxle assembly) connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
A66-27 (NOPM) - D68-2 (OPST)	Always	Below 1 Ω
A65-6 (OP21) - D68-4 (+B)	Always	Below 1 Ω
A66-27 (NOPM) - Body ground	Always	10 kΩ or higher
D68-2 (OPST) - Body ground	Always	10 kΩ or higher
A65-6 (OP21) - Body ground	Always	10 kΩ or higher
D68-4 (+B) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK ENGINE STOP AND START ECU (NOPM TERMINAL VOLTAGE)

Disconnect the D68 oil pump with motor assembly (automatic transaxle assembly) connector.

*a
Component with harness connected

(Engine Stop and Start ECU)
- -
Turn the engine switch on (IG).

Measure the voltage according to the value(s) in the table below.

Standard Voltage

Tester Connection	Condition	Specified Condition
A66-27 (NOPM) - A66-6 (DGND)	Engine switch on (IG)	10 to 14 V

Result

Proceed to
OK
NG

REPLACE AUTOMATIC TRANSAXLE ASSEMBLY for U661E: Click here for U661F: Click here

REPLACE ENGINE STOP AND START ECU Click here

PERFORM ACTIVE TEST USING GTS (AT OIL PUMP (LO))

Drive the vehicle to warm up the engine and automatic transaxle fluid.

Tech Tips

The oil pump with motor assembly (automatic transaxle assembly) may not operate properly if the automatic transaxle fluid temperature is low. Make sure to warm up the automatic transaxle fluid before performing the Active Test. (Automatic transaxle fluid temperature: 25°C (77°F) or higher)
Connect the GTS to the DLC3.
Turn the engine switch on (IG).

Tech Tips

Do not start the engine.
Turn the GTS on.
Enter the following menus: Powertrain / Stop and Start / Active Test / AT Oil Pump (Lo).

Check the operating sound of the oil pump with motor assembly (automatic transaxle assembly) while performing the Active Test.

Standard

AT Oil Pump (Lo)	Result
ON	Operating sound can be heard
OFF	Operating sound cannot be heard

Result

Proceed to
OK
NG

CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - OIL PUMP WITH MOTOR ASSEMBLY) Click here

CHECK ENGINE STOP AND START ECU (NOPM TERMINAL WAVEFORM)

Connect an oscilloscope to terminals A66-27 (NOPM) and A66-6 (DGND).

*a
Component with harness connected

(Engine Stop and Start ECU)
- -
Enter the following menus: Powertrain / Stop and Start / Active Test / AT Oil Pump (Lo).


*a	5 V/DIV.
*b	5 ms./DIV.

Check the waveform while performing the Active Test.

Item	Condition
Tester Connection	A66-27 (NOPM) - A66-6 (DGND)
Tool Setting	5 V/DIV., 5 ms./DIV.
Condition	Engine switch on (IG) (engine is stopped) Active Test "AT Oil Pump (Lo)" being performed

Standard
The waveform is similar to that shown in the illustration with no noise.

Result

Proceed to
OK
NG

REPLACE ENGINE STOP AND START ECU Click here

CHECK OIL PUMP WITH MOTOR ASSEMBLY (OPST TERMINAL VOLTAGE)

*a
Front view of wire harness connector

(to Oil Pump with Motor Assembly (Automatic Transaxle Assembly))

Disconnect the D68 oil pump with motor assembly (automatic transaxle assembly) connector.
Turn the engine switch on (IG).

Measure the voltage according to the value(s) in the table below.

Standard Voltage

Tester Connection	Condition	Specified Condition
D68-2 (OPST) - D68-1 (GND)	Engine switch on (IG)	10 to 14 V

Result

Proceed to
OK
NG

REPLACE AUTOMATIC TRANSAXLE ASSEMBLY for U661E: Click here for U661F: Click here

CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - OIL PUMP WITH MOTOR ASSEMBLY)

Disconnect the A66 engine stop and start ECU connector.
Disconnect the D68 oil pump with motor assembly (automatic transaxle assembly) connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
A66-27 (NOPM) - D68-2 (OPST)	Always	Below 1 Ω
A66-27 (NOPM) - Body ground	Always	10 kΩ or higher
D68-2 (OPST) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPLACE ENGINE STOP AND START ECU Click here

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - OIL PUMP WITH MOTOR ASSEMBLY)

Disconnect the A65 engine stop and start ECU connector.
Disconnect the D68 oil pump with motor assembly (automatic transaxle assembly) connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

for 8AR-FTS:
Tester Connection	Condition	Specified Condition
A65-6 (OP21) - D68-4 (+B)	Always	Below 1 Ω
A65-6 (OP21) - Body ground	Always	10 kΩ or higher
D68-4 (+B) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (OIL PUMP WITH MOTOR ASSEMBLY - BODY GROUND)

Disconnect the D68 oil pump with motor assembly (automatic transaxle assembly) connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
D68-1 (GND) - Body ground	Always	Below 1 Ω

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK ENGINE STOP AND START ECU (OP21 TERMINAL VOLTAGE)

Disconnect the D68 oil pump with motor assembly (automatic transaxle assembly) connector.

*a
Component with harness connected

(Engine Stop and Start ECU)
- -
Connect the GTS to the DLC3.
Turn the engine switch on (IG).

Tech Tips

Do not start the engine.
Turn the GTS on.
Enter the following menus: Powertrain / Stop and Start / Active Test / AT Oil Pump (Lo).

Powertrain > Stop and Start > Active Test

Tester Display

AT Oil Pump (Lo)

Measure the voltage according to the value(s) in the table below.

Standard Voltage

Tester Connection	Condition	Specified Condition
A65-6 (OP21) - A66-6 (DGND)	Engine switch on (IG) (engine is stopped) Active Test "AT Oil Pump (Lo)" being performed	10.5 to 16 V

Result

Proceed to
OK
NG

REPLACE ENGINE STOP AND START ECU Click here

CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - OIL PUMP WITH MOTOR ASSEMBLY)

Disconnect the A66 engine stop and start ECU connector.
Disconnect the D68 oil pump with motor assembly (automatic transaxle assembly) connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
A66-9 (OPM1) - D68-3 (SI)	Always	Below 1 Ω
A66-9 (OPM1) - Body ground	Always	10 kΩ or higher
D68-3 (SI) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK OIL PUMP WITH MOTOR ASSEMBLY (OPM1 TERMINAL WAVEFORM)

Connect an oscilloscope to the A66-9 (OPM1) and A66-6 (DGND) terminals of the engine stop and start ECU connector.

*a
Component with harness connected

(Engine Stop and Start ECU)
- -
Connect the GTS to the DLC3.
Turn the engine switch on (IG).

Tech Tips

Do not start the engine.
Turn the GTS on.
Enter the following menus: Powertrain / Stop and Start / Active Test / AT Oil Pump (Lo).

Powertrain > Stop and Start > Active Test

Tester Display

AT Oil Pump (Lo)


*a	5 V/DIV.
*b	5 ms./DIV.

Check the waveform while performing the Active Test.

Item	Condition
Tester Connection	A66-9 (OPM1) - A66-6 (DGND)
Tool Setting	5 V/DIV., 5 ms./DIV.
Condition	Engine switch on (IG) (engine is stopped) Active Test "AT Oil Pump (Lo)" being performed

Standard
The waveform is similar to that shown in the illustration with no noise.

Result

Proceed to
OK
NG

REPLACE ENGINE STOP AND START ECU Click here

REPLACE AUTOMATIC TRANSAXLE ASSEMBLY for U661E: Click here for U661F: Click here