2004 Civic ex 157,000 miles, Drives fine after initial start up. Once i reach 45-50 mph the ecu goes into limp mode. Wont go passed 3800 rpms if i shut the car off whiling driving and restart it, its fine for a while.

So I have checked:
oil level-clean and full
vtec solenoid - Opens and closes when power is applied
Vtec screen - clean
oil pressure- is within spec
wiring- good

Please help me out

 

Disconnect the VTEC oil pressure sensor and measure the sensor for continuity @ 3000rpm

no continuity @ 3000rpm or continuity below 3000rpm= bad oil pressure switch

continuity @ 3000rpm= short in the wires between the sensor and the ECM/PCM

 

The vtec solenoid and vtec oil pressure switch are brand new from honda dealer. but ill check

 

Oil pressure switch is operating fine. Switched it out with one that works fine on another 04 civic. Same problem.

 

What pin in the ecu is that sensor?

 

1. Disconnect battery terminals from the VTEC solenoid connector and disconnect ECM/PCM connector B (connector B is the second from the bottom while you're looking at the ECM/PCM in the dash)

2. Check for continuity between ECM/PCM connector terminal B9 (blue/black) and body ground

Is there continuity?

Yes- Repair the short in the wire between B9 and the oil pressure switch

NO- next step

3. Check for continuity between ECM/PCM connector terminal B15 (green/yellow) and body ground

Is there continuity?

YES- Repair the short in the wire between B15 and the VTEC solenoid

NO- nect step

4. At the solenoid valve connector, jump a wire from the harness side of the connector to body ground

5. Check for continuity between B15 and body ground

Is there continuity?

YES- update or replace ECM/PCM

NO- repair open between B15 and the solenoid

 

Thanks ill try it.

 

ok so i tested the wiring everything is fine there. the only time i have continuity is if b plug is plugged into the ecm.... my next step i think is to pull the valve cover and inspect the rocker arm assembly. i have heard there is a bolt/plug that goes in the head so a tech can check the oil pressure on the other side of the vtec solenoid.....

 

soo after looking at the rocker assembly i found the problem!!!!! the cars head gasket had been change by some one almost a year ago.. they torqued the head correctly but no the cam caps. i found 3 lose bolts which would allow the cam caps to move away from the cam...this is what cuzed the oil pressure to lower enough to through a code. tightened the bolts and no more problems all day!!!

Thanks lazlong for your help.