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Discussion Starter · #1 ·
Yesterday I got a P1578 - Brake System Failure along with P0171 and P0174. (P0171 and P0174 are ongoing intermittent codes.)

I can't find any good information on P1578 anywhere. Does anyone have any ideas?

This is related to my Brake Booster Thread.

Thank you!

Your Humble Administrator
2008 RAV4 Limited V6
16,887 Posts
Here's what the Toyota service manual says in the cruise control section:

P1578/69 Brake System Malfunction - VSC system see page CC-26

OK, so page CC-26 says:

(a) Check the DATA LIST for proper functioning of the stop
light switch.
(b) Remove the stop light switch.
(c) Measure the resistance of the switch.

(a) Remove the STOP and IGN fuses from the instrument
panel junction block.
(b) Remove the IG2 fuse from the engine room No. 1 relay
(c) Measure the resistance of the fuses.
Standard resistance:
Below 1 Ω

(a) Remove the IG2 relay from the instrument panel junction
(b) Measure the resistance of the relay.
Standard resistance: 10 kΩ or higher, Below 1 Ω
(when battery voltage is applied to
terminals 1 and 2)

Next it says to check various wiring harness connectors.

Super Moderator
11,068 Posts
Any trailer lights hookups on the car? I got several weird codes when I inadvertently disconnected the ground from mine. Reconnecting made them all go away.
I also suspect whatever is causing the abnormal hissing sound is directly connected and probably causing the issues. Maybe listen to another RAV4.
Also, why was the booster replaced? I've never heard of one failing on a RAV4.
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