NB_Si_Freak

My '00 Si has been plagued with throwing codes and weird electrical issues for a while -- VTEC sensor code, speedo varies erratically even while idling, etc.

But last week while cruising at 70 mph there was, for no apparent reason, no throttle response. I tried downshifting and still no power. Code P1259 was thrown before this occurred. My tach works, but the speedo and odometer are not functioning.

VTEC solenoid was replaced about 3 months ago and oil level is good (VTEC sensor screens checked too). Starting to wonder if it is an ECU issue, or something else.

Anyone got any ideas?! This is driving me

Fliptard

1. make sure there is oil in the engine
2. take the vtec pressure switch off the solenoid and spray out the hole in it.
3. check the plug for the speed sensor, making sure it's connected and none of the wires are broke/ corroded

Post your results

NB_Si_Freak

Oil was fine. Replaced VTEC solenoid with another (spare) one. Checked (removed and visually checked) VSS. Everything looked fine.

Reset the ECU. After running for 5 minutes, shut down and took it for a relaxed drive (not trying to kick VTEC in). Engine light came on again. Still no speedo, tach is fine.

Question: is the VTEC somehow reliant on the VSS signal? Wondering if I should R&R the VSS and see what happens. Can't test the harness easily to look for opens - would have to make up my own. Dealer wants around $300 just to test (not happening).

Any other ideas?

ezone

Yes, no, why?, and OMFG.

Connect a scanner, read codes.
Read the live data list while driving, see what the VSS value is and compare to what the speedo says.

A dead or funky speedo is common by itself. If there is no code in the computer for a lack of VSS input (P0500), it's probably just a bad speedo head.
Bang on the dash over the gauges while it's acting up, see if anything changes.

However, there is a TSB 00-081 that addresses
SYMPTOM
The speedometer needle fluctuates between 50 and 65
mph, or it sticks at 40 mph

Fliptard

vtec will not engage if the VSS is not working correctly.

change the VSS or at least just the head part of it and see if that fixes the speedo

NB_Si_Freak

Final update:
- Checked everything VTEC-wise: all in good shape.
- Changed the VSS

Results:
- Speedo and odometer now work
- VTEC is now kicking in
- Motor runs like the B series it is!

Thanks for the assistance -- now off to burn up some roads!