Fi code 25 - Knock Sensor

vinnyst1300

Hi guys,
My 2003 ST1300 Fi light recently lite up. I checked the error code and it was 25, which I thought it was the left sensor. Just to be sure, I pulled the plug on the right, ran the engine at 4000RPM and the error code 26 showed up...so I know it is the left hand side.
Checked the wire on the left looked clean.
I unplugged the sensor and the ECM and checked for continuity from the plug where the sensor is to the plug where the ECM is and it showed 0.00V on my meter...so wire is not broken.
I plugged back the ECM and turned ignition key to "on" but without starting the engine and measured the voltage at the plug where the sensor is, and it showed 0.25V which gave me an indication the wire is not shorted out or broken somewhere. I did the same to the wire on the RH sensor and got exactly the same results. So wires look good.
I replaced the LH sensor with a brand new sensor. cranked up the engine, rev up to 400RPM and code 25 showed up.
My question is:
1. If the error code changes from 25 to 26 when I unplugged the respective sensors, is there a possibility the ECM can still be BAD?
I am thinking of changing the sub-harness just to be sure and if still not work then a new ECM.
Anyone has any suggestion? Thanks in advance
 
vinnyst1300 said:
If the error code changes from 25 to 26 when I unplugged the respective sensors, is there a possibility the ECM can still be BAD?
Click to expand...

25 and 26 are separate error codes. If both sensors are disconnected, you should get both codes.

There have been ECMs that have had the knock sensor circuits fail, but I'd run down all of the wiring and so forth first. A good cleaning of all of the contact surfaces probably wouldn't hurt before you really start digging.

--Mark
 
Man , make sure you get this issue fixed ! The ECM not reading the anti-knock sensors on my new BMW R1200RT back in 2008 is what ruined the engine in less than 6K miles - predetonation causing piston slap !
 
iirc heat damaged wires/connectors and mice are the typical suspects.
search the board honda got the left and right codes swapped at one point.
do you have the service manual?
 
Does anyone know the part number for the sub-harness that has the connectors for the KNOCK SENSORS?
I found two numbers:
1. In the crankcase section, I found 32109-MCS-010 (SUB-WIRE, ENGINE)
2. In the Wire Harness section, I found 32103-MCS-770 (SUB-HARNESS, INJECTOR)
I wonder which one is the correct one for the knock sensors
 
Thanks guys for the info. Waiting for the sub-harness to arrive and will update...
 
I cleared all the faulty codes from the ECM. Restarted the engine and kept under 4000rpm NO faulty code. Over 4000rpm again. Does this mean that under 4000rpm the knock sensor is not needed and only supposed to function when engine is over 4000rpm?
 
The knock sensor alarm is set up for 3900 RPM or higher for 10 seconds. There is less danger of engine damage at lower RPM. The knock sensor is always functioning.
 
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