STOP AND START SYSTEM, Diagnostic DTC:P2531

DTC Code	DTC Name
P2531	Ignition Switch Run Position Circuit Low

DESCRIPTION

When the engine stop and start ECU receives the OFF signal from the ignition or starter switch assembly*1 or certification ECU (smart key ECU assembly)*2 when communication with the ECM is normal, the engine stop and start ECU stores DTC P2531.

*1: w/o Entry and Start System
*2: w/ Entry and Start System

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Warning Indicate	Memory
P2531	Ignition Switch Run Position Circuit Low	Both of the following conditions continue for 10 seconds or more (1 trip detection logic): Ignition switch off signal is input. Communication with the ECM is normal.	Wire harness or connector IG2 relay (w/ Entry and Start System) Instrument panel junction block assembly (EFI-MAIN NO. 1, EFI-MAIN NO. 2 relay) Ignition or starter switch assembly (w/o Entry and Start System) Certification ECU (Smart key ECU assembly) (w/ Entry and Start System) Engine stop and start ECU	Does not come on	DTC stored

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Warning Indicate

Memory

P2531

Ignition Switch Run Position Circuit Low

Both of the following conditions continue for 10 seconds or more (1 trip detection logic):

Ignition switch off signal is input.
Communication with the ECM is normal.

Wire harness or connector
IG2 relay (w/ Entry and Start System)
Instrument panel junction block assembly (EFI-MAIN NO. 1, EFI-MAIN NO. 2 relay)
Ignition or starter switch assembly (w/o Entry and Start System)
Certification ECU (Smart key ECU assembly) (w/ Entry and Start System)
Engine stop and start ECU

Does not come on

DTC stored

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

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 with the battery temperature at 11°C (51°F) or higher for 5 to 60 minutes 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".)
- 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 the engine warms up and check that the engine speed is within 50 rpm of the target idle speed.
CONFIRMATION AFTER TROUBLESHOOTING
1. Connect the GTS to the DLC3.
2. Turn the ignition switch to ON and turn the GTS on.
3. Clear the DTCs.
  
  Click here
  
  Powertrain > Stop and Start > Clear 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 the confirmation driving pattern, obey all speed limits and traffic laws.
6. for Automatic Transmission:
  
  Depress the brake pedal and stop the vehicle.
  
  for Manual Transmission:
  
  Stop the vehicle, move the shift lever to neutral and release the clutch pedal.
7. Keep the engine stopped by stop and start control for 10 second or more. (for Automatic Transmission: Keep the shift lever in D.)
8. for Automatic Transmission:
  
  Release the brake pedal with the shift lever in D to start the engine.
  
  for Manual Transmission:
  
  Depress the clutch pedal and start the engine.
  
  Tech Tips
  
  If the engine cranks slowly when the engine is restarted, it can be determined that the battery voltage is low.
9. Check that DTCs are not output.
  
  Click here
  
  Powertrain > Stop and Start > Trouble Codes
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 with the battery temperature at 11°C (51°F) or higher for 5 to 60 minutes 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".)
- 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.
STOP AND START SYSTEM OPERATION CHECK
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 the confirmation driving pattern, obey all speed limits and traffic laws.
4. for Automatic Transmission:
  
  Depress the brake pedal and stop the vehicle.
  
  for Manual Transmission:
  
  Stop the vehicle, move the shift lever to neutral and release the clutch pedal.
5. Allow the engine to stop by stop and start control. (for Automatic Transmission: Keep the shift lever in D.)
6. for Automatic Transmission:
  
  Release the brake pedal with the shift lever in D to start the engine.
  
  for Manual Transmission:
  
  Depress the clutch pedal and start the engine.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

Note

Before replacing the engine stop and start ECU, read the number of starter operations and total number of engine starts 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 or airbag sensor assembly, clear and calibrate the deceleration sensor zero point in the engine stop and start ECU.

Click here
for Automatic Transmission:

When the engine stop and start ECU is replaced, check the electromagnetic oil pump.

Click here
Inspect the fuses for circuits related to this system before performing the following procedure.

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

READ VALUE USING GTS (IG SWITCH)

Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Turn the GTS on.
Enter the following menus: Powertrain / Stop and Start / Data List / IG Switch.

Powertrain > Stop and Start > Data List

Tester Display

IG Switch

Tester Display
IG Switch

Read the value displayed on the GTS.

Result

Tester Display	Result	Proceed to
IG Switch	OFF	A
IG Switch	ON	B

USE SIMULATION METHOD TO CHECK Click here

CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

Disconnect the G127 engine stop and start ECU connector.
Disconnect the 2P instrument panel junction block assembly connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
G127-18 (IG2) - 2P-6	Always	Below 1 Ω
G127-18 (IG2) - Body ground	Always	10 kΩ or higher
2P-6 - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK (w/ Entry and Start System)
OK (w/o Entry and Start System)
NG

OK (w/o Entry and Start System)

CHECK HARNESS AND CONNECTOR (IGNITION OR STARTER SWITCH ASSEMBLY AM2 TERMINAL VOLTAGE) Click here

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK (w/ Entry and Start System)

CHECK HARNESS AND CONNECTOR (IG2 RELAY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

Disconnect the 2G instrument panel junction block assembly connector.
Remove the IG2 relay from No. 4 relay block assembly.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
2G-1 - IG2 relay terminal 3	Always	Below 1 Ω
2G-1 - Body ground	Always	10 kΩ or higher
IG2 relay terminal 3 - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

INSPECT RELAY (IG2 RELAY)

Inspect the IG2 relay.

Click here

Result

Proceed to
OK
NG

REPLACE RELAY (IG2 RELAY)

CHECK HARNESS AND CONNECTOR (IG2 RELAY - BATTERY, BODY GROUND)

*1	for RHD	*2	for LHD
*3	No. 4 Relay Block ASSEMBLY	-	-
*a	IG2 Relay Terminal	-	-

Remove the IG2 relay from No. 4 relay block assembly.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
IG2 relay terminal 5 - Body ground	Always	11 to 14 V

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

Standard Resistance

Tester Connection	Condition	Specified Condition
IG2 relay terminal 2 - Body ground	Always	Below 1 Ω

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (IG2 RELAY - CERTIFICATION ECU (SMART KEY ECU ASSEMBLY))

Remove the IG2 relay from No. 4 relay block assembly.
Disconnect the G69 certification ECU (smart key ECU assembly) connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
G69-20 (ID1D) - IG2 relay terminal 1	Always	Below 1 Ω
G69-20 (ID1D) - Body ground	Always	10 kΩ or higher
IG2 relay terminal 1 - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) +B TERMINAL VOLTAGE)

Disconnect the G69 certification ECU (smart key ECU assembly) connector.

*a	Front view of wire harness connector (to Certification ECU (Smart Key ECU Assembly))

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

Standard Voltage

Tester Connection	Condition	Specified Condition
G69-1 (+B) - Body ground	Always	11 to 14 V

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) IG1D TERMINAL VOLTAGE)

*a	Component with harness connected (Certification ECU (Smart Key ECU Assembly))

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

Standard Voltage

Tester Connection	Condition	Specified Condition
G69-20 (IG1D) - Body ground	Ignition switch ACC	Below 1 V
G69-20 (IG1D) - Body ground	Ignition switch ON	9 V or higher

Result

Proceed to
OK
NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

CHECK HARNESS AND CONNECTOR (ENGINE STOP AND START ECU - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

Disconnect the G126 engine stop and start ECU connector.
Disconnect the 2G instrument panel junction block assembly connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
G126-1 (+B) - 2G-3	Always	Below 1 Ω
G126-1 (+B) - Body ground	Always	10 kΩ or higher
2G-3 - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY (EFI-MAIN NO. 1 RELAY - EFI-MAIN NO. 2 RELAY))

Disconnect the 2P and 2G instrument panel junction block assembly connectors.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
2P-9 - 2G-7	Always	Below 1 Ω
2P-9 - Body ground	Always	10 kΩ or higher
2G-7 - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY - BATTERY, BODY GROUND)

Front view of wire harness connector

(to Instrument Panel Junction Block Assembly)

Disconnect the instrument panel junction block assembly connectors.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
2B-1 - Body ground	Always	11 to 14 V

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

Standard Resistance

Tester Connection	Condition	Specified Condition
2J-5 - Body ground	Always	Below 1 Ω
2K-3 - Body ground	Always	Below 1 Ω

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK ECM (IGSW TERMINAL VOLTAGE)

*a
Front view of wire harness connector

(to ECM)

Disconnect the G86 ECM connector.
Turn the ignition switch to ON.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
G86-18 (IGSW) - Body ground	Ignition switch ON	9.5 to 14 V

Result

Proceed to
OK
NG

CHECK HARNESS AND CONNECTOR (ECM - INSTRUMENT PANEL JUNCTION BLOCK) Click here

CHECK HARNESS AND CONNECTOR (EFI-MAIN RELAY - ECM)

Disconnect the 2P instrument panel junction block assembly connector.
Disconnect the G85 ECM connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
2P-8 - G85-14 (MREL)	Always	Below 1 Ω
2P-8 - Body ground	Always	10 kΩ or higher
G85-14 (MREL) - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

INSPECT ECM (MREL VOLTAGE)

*a
Component with harness connected

(ECM)

Turn the ignition switch to ON.

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

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
G85-14 (MREL) - Body ground	Ignition switch ON	11 to 14 V

Result

Proceed to
OK
NG

GO TO ECM POWER SOURCE CIRCUIT Click here

INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY (EFI-MAIN NO. 1 RELAY, EFI-MAIN NO. 2 RELAY)

Inspect instrument panel junction block assembly (EFI-MAIN NO. 1 relay, EFI-MAIN NO. 2 relay).

Click here

Result

Proceed to
OK
NG

REPLACE ENGINE STOP AND START ECU Click here

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

CHECK HARNESS AND CONNECTOR (ECM - INSTRUMENT PANEL JUNCTION BLOCK)

Disconnect the 2G instrument panel junction block connector.
Disconnect the G86 ECM connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
G86-18 (IGSW) - 2G-2	Always	Below 1 Ω
G86-18 (IGSW) - Body ground	Always	10 kΩ or higher
2G-2 - Body ground	Always	10 kΩ or higher

Result

Proceed to
OK
NG

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR

CHECK HARNESS AND CONNECTOR (IGNITION OR STARTER SWITCH ASSEMBLY AM2 TERMINAL VOLTAGE)

Disconnect the ignition or starter switch assembly connector.

*a	Front view of wire harness connector (to Ignition or Starter Switch Assembly)

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

Standard Voltage

Tester Connection	Condition	Specified Condition
G1-4 (AM2) - Body ground	Always	11 to 14 V

Result

Proceed to
OK
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

INSPECT IGNITION OR STARTER SWITCH ASSEMBLY

Inspect the ignition or starter switch assembly.

Click here

Result

Proceed to
OK
NG

REPLACE IGNITION OR STARTER SWITCH ASSEMBLY Click here

CHECK HARNESS AND CONNECTOR (IGNITION OR STARTER SWITCH ASSEMBLY - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

Disconnect the 2G instrument panel junction block assembly connector.

*a	Front view of wire harness connector (to Instrument Panel Junction Block Assembly)

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

Standard Voltage

Tester Connection	Condition	Specified Condition
2G-1 - Body ground	Ignition switch ON	11 to 14 V

Result

Proceed to
OK
NG

GO TO STEP 9 Click here

REPAIR OR REPLACE HARNESS OR CONNECTOR