Lexus NX: DC / DC Converter Status Circuit Low Input (P0A09-591)
DESCRIPTION
The DC/DC converter varies output voltage based on voltage change signals (VLO signal line) received from the hybrid vehicle control ECU.
If the vehicle is being driven with an inoperative DC/DC converter, the voltage of the auxiliary battery will drop, which will prevent the continued operation of the vehicle. Therefore, the hybrid vehicle control ECU monitors the operation of the DC/DC converter and alerts the driver if it detects a malfunction.
| DTC No. | Detection Item | DTC Detection Condition | Trouble Area | MIL | Warning Indicate |
|---|---|---|---|---|---|
| P0A09-591 | DC / DC Converter Status Circuit Low Input | Open or short to ground in the signal line of DC/DC converter (VLO) (1 trip detection logic) |
| Does not come on | Master Warning Light: Comes on |
WIRING DIAGRAM
CAUTION / NOTICE / HINT
CAUTION:
- Before inspecting the high-voltage system or disconnecting the low voltage connector of the inverter with converter assembly, take safety precautions such as wearing insulated gloves and removing the service plug grip to prevent electrical shocks. After removing the service plug grip, put it in your pocket to prevent other technicians from accidentally reconnecting it while you are working on the high-voltage system.
-
After removing the service plug grip, wait for at least 10 minutes before touching any of the high-voltage connectors or terminals. After waiting for 10 minutes, check the voltage at the terminals in the inspection point in the inverter with converter assembly. The voltage should be 0 V before beginning work.
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HINT:
Waiting for at least 10 minutes is required to discharge the high-voltage capacitor inside the inverter with converter assembly.
NOTICE:
After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.
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HINT:
After the repair, clear the DTCs and perform the following procedure to check that DTCs are not output.
- Turn the power switch on (IG) and wait for 10 seconds or more.
PROCEDURE
| 1. | CHECK CONNECTOR CONNECTION CONDITION (HYBRID VEHICLE CONTROL ECU CONNECTOR) |
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| NG | .gif) | CONNECT SECURELY |
|
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| 2. | CHECK CONNECTOR CONNECTION CONDITION (INVERTER WITH CONVERTER ASSEMBLY CONNECTOR) |
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| Result | Proceed to |
|---|---|
| OK | A |
| NG (The connector is not connected securely.) | B |
| NG (The terminals are not making secure contact or are deformed, or water or foreign matter exists in the connector.) | C |
| B | | CONNECT SECURELY |
| C | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
|
| 3. | CHECK HYBRID VEHICLE CONTROL ECU (CHECK WAVEFORM) |
(a) Connect an oscilloscope between the hybrid vehicle control ECU terminals specified in the table below.
(b) Turn the power switch on (IG).
| (c) Measure the waveform.
OK: The waveform appears as shown in the illustration. HINT:
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(d) Turn the power switch off.
| NG | | GO TO STEP 6 |
|
| 4. | CLEAR DTC |
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| 5. | CHECK DTC OUTPUT (HYBRID CONTROL) |
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (READY).
(c) Enter the following menus: Powertrain / Hybrid Control / Trouble Codes.
(d) Check for DTCs.
Powertrain > Hybrid Control > Trouble Codes| Result | Proceed to |
|---|---|
| P0A09-591 is not output. | A |
| P0A09-591 is output again. | B |
(e) Turn the power switch off.
| A | | CHECK FOR INTERMITTENT PROBLEMS |
| B | | REPLACE HYBRID VEHICLE CONTROL ECU |
| 6. | CHECK HARNESS AND CONNECTOR (RESISTANCE VALUE OF VLO INSIDE HYBRID VEHICLE CONTROL ECU) |
CAUTION:
Be sure to wear insulated gloves.
(a) Check that the service plug grip is not installed.
NOTICE:
After removing the service plug grip, do not turn the power switch on (READY), unless instructed by the repair manual because this may cause a malfunction.
(b) Disconnect the A59 inverter with converter assembly connector.
| (c) Measure the resistance according to the value(s) in the table below. Standard Resistance:
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|
(d) Reconnect the A59 inverter with converter assembly connector.
| OK | | REPLACE INVERTER WITH CONVERTER ASSEMBLY |
|
| 7. | CHECK HARNESS AND CONNECTOR (INVERTER WITH CONVERTER ASSEMBLY - HYBRID VEHICLE CONTROL ECU) |
CAUTION:
Be sure to wear insulated gloves.
(a) Check that the service plug grip is not installed.
NOTICE:
After removing the service plug grip, do not turn the power switch on (READY), unless instructed by the repair manual because this may cause a malfunction.
(b) Disconnect the A59 inverter with converter assembly connector.
(c) Disconnect the A60 hybrid vehicle control ECU connector.
| (d) Measure the resistance according to the value(s) in the table below. Standard Resistance:
|
|
(e) Reconnect the A60 hybrid vehicle control ECU connector.
(f) Reconnect the A59 inverter with converter assembly connector.
| OK | | REPLACE HYBRID VEHICLE CONTROL ECU |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR |
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