EPS Warning Light Circuit [09/2014 - ]: Procedure
- CHECK ASSIST LIMIT RECORD
- Using the Techstream, read the Data List item "Assist Limit Record 1".
Chassis > EMPS > Data List
Tester Display Measurement Item Range Normal Condition Diagnostic Note Assist Limit Record 1 Information of assist limit that was used in the past or is currently in use (latest history) Unrec, Mtr Overheat, Pow Vol Low, Pow Vol Low Prevent, Eng Stall, Ready OFF, Mtr Overload, Vhcl Spd Sig Malf, Batt Vol Keep - - Chassis > EMPS > Data List
Tester Display Assist Limit Record 1 HINT:
For the Data List item "Assist Limit Record 1", each item in the Range is described below.
Range Description Mtr Overheat When the vehicle is stopped or traveling at low speed, and steering operations are performed repeatedly or the steering wheel is turned all the way to the side and held there for a long time, assist may be limited in order to prevent overheating of the power steering motor assembly and power steering ECU assembly.
After 10 minutes elapse with the engine stopped and no steering operations being performed, the system will return to normal.
After recovering from the overheated condition, assist can be performed as usual.Pow Vol Low When insufficient battery charge, or battery degradation etc. causes the voltage to temporarily decrease, assist may be stopped.
After the battery condition returns to normal, assist can be performed as usual.Pow Vol Low Prevent When insufficient battery charge, or battery degradation etc. causes the voltage to temporarily decrease, assist may be limited.
After the battery condition returns to normal, assist can be performed as usual.Eng Stall When the engine stalls, battery charge becomes insufficient, so assist is stopped.
After recovering from the engine stall, assist can be performed as usual.Ready OFF After Ready ON, if a malfunction in the HV system etc. causes a return to Ready OFF, the HV battery charge becomes insufficient, so assist is stopped.
After returning to Ready ON state, assist can be performed as usual.Mtr Overload When the steering wheel cannot turn, such as when a road wheel is against a curb, if the driver continues to apply force to the steering wheel, current to the motor may be limited to prevent overheating.
When the steering wheel is returned to a neutral position, assist can be performed as usual.DC-DC Malf If there is a malfunction in the DC-DC converter, etc., assist may be limited.
After the DC-DC converter returns to normal, assist can be performed as usual.Vhcl Spd Sig Malf If the vehicle speed signal is abnormal due to a wheel speed sensor malfunction, etc., assist may be limited. Batt Vol Keep When insufficient battery charge, or battery degradation etc. causes the voltage to temporarily decrease, assist may be limited.
After the battery condition returns to normal, assist can be performed as usual. - Based on the "Assist Limit Record 1" information, the following Data List items and the information from the customer interview, explain the situation to the customer.
Chassis > EMPS > Data List
Tester Display Measurement Item Range Normal Condition Diagnostic Note Record 1 Key Cycle Number of times that the engine switch was turned on (IG) before Assist Limit Record 1 was stored Min.: 0 times
Max.: 65535 times- - Record 1 Key Cycle Elapsed Time Period of time that elapsed since the engine switch was turned on (IG) before Assist Limit Record 1 was stored Min.: 0.0 s
Max.: 53687091.1 s- - Chassis > EMPS > Data List
Tester Display Record 1 Key Cycle Record 1 Key Cycle Elapsed Time Result
Result Proceed to "Unrec" is displayed A Other than Unrec is displayed B HINT:
If it is necessary to investigate further into the past, check the "Assist Limit Record 2" and "Assist Limit Record 3" information in the same way as "Assist Limit Record 1".
Result:
B
EXPLAIN THE CHECKED "ASSIST LIMIT RECORD 1" TO THE CUSTOMER, CROSS-CHECKING THE DATA LIST ITEMS WITH THE INFORMATION FROM THE CUSTOMER INTERVIEW.
Result:
A
See step 2
- Using the Techstream, read the Data List item "Assist Limit Record 1".
- CHECK HARNESS AND CONNECTOR
- Jiggle the power steering ECU assembly connectors and wire harness up and down, and left and right to check the illumination condition of the EPS warning light in the combination meter assembly.
OK
The EPS warning light illumination condition does not change.
HINT:
When the EPS warning light is operating properly, it comes on when the engine switch is turned on (IG) and goes off when the engine is started.
Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
Result:
OK
See step 3
- Jiggle the power steering ECU assembly connectors and wire harness up and down, and left and right to check the illumination condition of the EPS warning light in the combination meter assembly.
- CHECK CAN COMMUNICATION SYSTEM
- Check for DTCs.
Refer to DIAGNOSIS SYSTEM [09/2014 - 08/2016] , or refer to DIAGNOSIS SYSTEM [08/2016 - 11/2017] , or refer to DIAGNOSIS SYSTEM [11/2017 - 03/2019] , or refer to DIAGNOSIS SYSTEM [03/2019 - 09/2020] , or refer to DIAGNOSIS SYSTEM [09/2020 - 01/2023] , or refer to DIAGNOSIS SYSTEM [01/2023 - 10/2023] , or refer to DIAGNOSIS SYSTEM [10/2023 - ]
Result
Result Proceed to CAN communication system DTCs are not output. A CAN communication system DTCs are output. B
Result:
B
GO TO CAN COMMUNICATION SYSTEM. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [09/2014 - 11/2017] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [11/2017 - 03/2019] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [03/2019 - 01/2023] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [01/2023 - ]
Result:
A
See step 4
- Check for DTCs.
- CHECK HARNESS AND CONNECTOR (IG POWER SUPPLY - GROUND)
- Disconnect the A18 power steering ECU assembly connector.
- Measure the voltage according to the value(s) in the table below.
Standard Voltage
Tester Connection Condition Specified Condition A18-14 (IG) - Body ground Engine switch on (IG) 8 to 16 V *a Front view of wire harness connector
(to Power Steering ECU Assembly) - Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition A18-9 (PGND) - Body ground Always Below 1 Ω Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
Result:
OK
See step 5
- INSPECT EPS RELAY (ELECTRIC POWER STEERING RELAY)
- Remove the EPS relay (electric power steering relay) from the No. 1 engine room relay block and No. 1 junction block assembly.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition 5 - 3 Voltage not applied between terminals 1 and 2 10 kΩ or higher 5 - 3 Voltage applied between terminals 1 and 2 Below 1 Ω 1 - 3 Voltage not applied between terminals 1 and 2 10 kΩ or higher 2 - 5 Voltage not applied between terminals 1 and 2 10 kΩ or higher 1 - 2 Voltage not applied between terminals 1 and 2 180 to 220 Ω *a EPS Relay (Electric Power Steering Relay) Result
Proceed to OK NG
Result:
NG
REPLACE EPS RELAY (ELECTRIC POWER STEERING RELAY)
Result:
OK
See step 6
- CHECK HARNESS AND CONNECTOR (BATTERY - NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY)
- Measure the voltage according to the value(s) in the table below.
*a No. 1 Engine Room Relay Block and No. 1 Junction Block Assembly *b EPS Relay (Electric Power Steering Relay) Standard Voltage
Tester Connection Condition Specified Condition 1 - Body ground Always 9 to 16 V 5 - Body ground Always 9 to 16 V Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
Result:
OK
See step 7
- Measure the voltage according to the value(s) in the table below.
- CHECK HARNESS AND CONNECTOR (NO. 1 ENGINE ROOM RELAY BLOCK AND NO. 1 JUNCTION BLOCK ASSEMBLY - POWER STEERING ECU ASSEMBLY)
- Disconnect the A18 power steering ECU assembly connector.
- Measure the resistance according to the value(s) in the table below.
Standard Resistance
Tester Connection Condition Specified Condition A18-10 (PIG) - 3 (No. 1 engine room relay block and No. 1 junction block assembly) Always Below 1 Ω A18-12 (RLY) - 2 (No. 1 engine room relay block and No. 1 junction block assembly) Always Below 1 Ω A18-10 (PIG) or 3 (No. 1 engine room relay block and No. 1 junction block assembly) - Body ground Always 10 kΩ or higher A18-12 (RLY) or 2 (No. 1 engine room relay block and No. 1 junction block assembly) - Body ground Always 10 kΩ or higher Result
Proceed to OK NG
Result:
NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
Result:
OK
See step 8
- INSPECT COMBINATION METER ASSEMBLY
- Reconnect the A18 power steering ECU assembly connector.
- Perform the Active Test of the combination meter assembly using the Techstream.
Body Electrical > Combination Meter > Active Test
Tester Display Indicat. EPS - Check the combination meter assembly.
OK
The EPS warning light turns on or off in accordance with the Techstream operation.
Result
Proceed to OK NG
Result:
OK
REPLACE POWER STEERING ECU ASSEMBLY. Refer to REMOVAL [09/2014 - ]
Result:
NG
GO TO METER / GAUGE SYSTEM. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [09/2014 - ]