Code No.31: ASTC-ECU power supply system (open circuit or short circuit)
OPERATION
In the ignition switch B circuit, the ASTC-ECU power is
supplied to the ASTC-ECU (terminal 9) from the ignition switch (IG2) through
the multi-purpose fuse number 22 in the junction block.
DIAGNOSIS CODE SET CONDITIONS
Diagnosis code No.31 is set if the
ignition switch B circuit is open or the internal circuit of the ASTC-ECU is
defective.
PROBABLE CAUSES
- Damaged wiring harness or connector
- Malfunction of the ASTC-ECU
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STEP 1. Check ASTC-ECU connector D-233 for loose, corroded or damaged
terminals, or terminals pushed back in the connector.
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Q.
Is the check result normal?
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 Go to Step 2.
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 Repair it. Then go to Step
6.
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STEP 2. Check the power supply circuit at ASTC-ECU harness connector
D-233.
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(1)Disconnect ASTC-ECU connector D-233 and measure at the
harness connector (harness side).
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(3)Measure the voltage between terminal 9 and body
earth.
OK: Approx. 12 volts (battery positive
voltage)
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Q.
Is battery positive voltage (approx. 12 volts) present?
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Go to Step 5.
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Go to Step 3.
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STEP 3. Check intermediate connector D-231 for loose, corroded or
damaged terminals, or terminals pushed back in the
connector.
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Q.
Is the check result normal?
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Go to Step 4.
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Repair or replace it. Then go to
Step 6.
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STEP 4. Check the harness wires between ASTC-ECU connector D-233
(terminal 9) and multi-purpose fuse number 22 (fuse box).
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Q.
Is the check result normal?
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Go to Step 6.
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Repair or replace it. Then go to
Step 6.
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STEP 5. Recheck for diagnosis code.
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(1)Erase the diagnosis code.
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(2)Recheck for diagnosis code.
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Replace the ASTC-ECU (Refer to
GROUP 35C, ASTC-ECU  ). Then go to Step 6.
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It can
be assumed that this malfunction is intermittent. Refer to GROUP 00, How to
Use Troubleshooting/Inspection Service Points - How to Cope
with Intermittent Malfunction .
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STEP 6. Recheck for diagnosis code.
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(1)Erase the diagnosis code.
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(2)Recheck for diagnosis code.
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Start over at Step 1.
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The
procedure is complete.
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