As far as I know, here are the possible causes for a car running in
safety boost.
-Engine is cold
-Bad Engine Temperature sensor
-Car is detonating
-Bad detonation sensor
Engine is cold-
Normal condition : no error code on ECU diagnostics. Until the car
reaches 60 C, the car will stay in safety mode. As soon as the temp is
above 60 C, you'll get full boost. You won't have to restart the car to
get full boost
Bad Engine Temperature Sensor-
Abnormal condition : should trigger code 13 but may trigger no error
code on ECU diagnostics. Your engine is hot, but the sensor is sending
"cold engine" info to the ECU. Your car will stay in safety boost. If the
sensor connectors are corroded (and based on experience), it's possible
that the sensor is sending bad info, even if you
won't get a code 13. If you do get a code 13, it's either the connectors
are badly corroded, or that the sensor is defective.
Car is detonating-
Normal condition : no error code on ECU diagnostics. This is probably
the WORST thing you can get, do something, NOW !! The sensor will only
detect detonation UNDER 3500 rpm, past that point, you're alone! If you
get detonation, the ECU considers it a "normal" condition, and will NOT
display any error code. It'll put the car in safety
mode, until you re-cycle the ignition. So, if you hit safety boost,
turn off the engine, restart it, and have no problem, it *might* be because
you get detonation. How to get rid of detination? Basically:
-Lower the boost
-Get colder plugs - PFR6B-11B
-Get new fuel filter
-Retard the timing
-Use better gas if available (or octane booster)
Bad detonation sensor-
ABNORMAL PERMANENT condition : error code 34 on ECU diagnostics. It's
not that the car is detonating, but that your SENSOR has a problem. You
will always get a code 34, and your car will ALWAYS be in safety boost
mode.I wrote an "how to" about it, located at here.
If someone worked on your engine (removing it), you probably get it because
they forgot to reconnect it, or because they re-painted the block, and
thus you get a bad connection.
ABNORMAL INTERMITTENT condition : should trigger error code 34 on ECU
diagnostics, may trigger no error code. WARNING, the following is speculation
on my side , and the "best" explanation I've found do far for some safety
boost gremlins, I confronted the ideas with other IZCC experts, and they
found it plausible:
Probable Cause:
The detonation sensor is simply screwed in the engine block. One wire
going to it (do NOT beleive what's written in the Nissan manuals, the TEXT
is incorrect, but the wiring diagram is correct), and the ground connection
being made through the engine block. From an electronic point of view,
I can understand WHY they decided to do that, but from a connection point
of view, having TWO wires would have been a LOT better.
Here's what MIGHT happen:
You have a "so so" connection from the det. sensor to the engine block.
The connection is good enough that the ECU cannot detect the sensor is
bad, but it's indeed NOT sending good info. So, you might be in a situation
where your det.sensor is out, but no error code. Also, while the engine
is cold, the sensor will send erroneous data, and the ECU "may" interpret
it as detonation, and activate safety boost....so you'll have to stop/restart
the engine to get out of it.
But, as the engine got hotter, metal expanded a little, and it's possible
that the electrical connection to the det.sensor is now better (or worse,
you decide), and thus the ECU will NOT trigger the safety boost anymore....
Troubleshooting for mechanical problems:
1. Do an ECU check. If you have an error code, fix the problem (you
cannot start a debug session with a known error)
2. If no error code... Run the car, be sure to get boost under 3500
rpm, check ECU
3. First clean the temp sensor, as it's the simplest one to have access
to, check ECU
4. Run the car, be sure to get boost under 3500 rpm ...check ECU
5. No safety boost ? problem fixed.. If safety boost ? next step
6. Reduce boost, Retard timing, pour some octane booster
7. Run the car, be sure to get boost under 3500 rpm ...check ECU
8. No safety boost, your car was detonating (probably)
9. Still Safety boost ? (bummer!!) Go here.
Read all the warnings, understand them, then BYPASS the det. sensor. If
you ever decide to BYPASS the det. sensor, you better really understand
the warnings, because if you destroy your engine, it'll be too bad for
you. SARCASTIC NOTE : For the "I sue faster than I drive" guys, I'm not
located in the US, so I'm totally immune to the US laws....got the message?
10. Run the car, be sure to get boost under 3500 rpm ...check ECU
11. No error code, no safety boost : probably have an intermittent problem
with det.sensor....sorry, cannot help you any
further...you decide to permanently bypass it (IMHO not a good idea),
or have it replaced (IMHO much better) No error code, safety boost : Well,
the problem CANNOT come from the det. sensor, so you have a problem with
the engine
temp sensor....re-clean it, or change it....
H. Le Hir
