NSX 1991

P 1259 VTEC oil pressure switch circuit or vtec solenoid or valve,Here the situation you can be dealing with the oil pressure switch or the VTEC solenoid or valve,

This is an error code related to VTEC related Honda engines. I am sending you a little reading on that error code.. Best of Luck..


The Check Engine Light (CEL) is on. Trouble code P1259. Tests/Procedures: 1. Locate the Variable Timing/Lift Control (VTEC) pressure switch, on the back of the cylinder block, by the oil filter.

2. The VTEC oil switch is normally closed and grounds the reference voltage from the Engine Control Module (ECM) on the Blue/Black (BLU/BLK) wire.

3. At approximately 4000 RPM, and when driving the vehicle, the VTEC system should turn on. To turn the system on, the ECM energizes the VTEC Solenoid valve and it allows oil pressure into the intake valve rocker arms, the oil pressure opens the VTEC oil pressure switch so the ECM can verify that VTEC did turn on correctly.

4. The code will set below 4000 RPM if the reference voltage is not grounded. The code will set above 4000 RPM if the VTEC oil switch does not open.

5. If the code sets at 4000 RPM or higher, the problem can be a low oil level or pressure, or a malfunction in the VTEC assembly. Potential Causes: Low Engine Oil
Plugged Oil Passage
Insufficient Oil Pressure
Plugged Oil Screen
Insufficient Oil Volume
Malfunctioning VTEC Oil Pressure Switch
Defective VTEC Solenoid
Tech Tips: When the P1259 code sets at 4,000 RPM or higher, always verify that the engine oil level is full. Also, if there is an oil pressure or volume problem, always verify that the oil pan is not pushed up and is too close to the oil pickup tube, causing an oil volume problem. Be very careful when supporting the engine with the oil pan.

TELL ME WHAT CHECK ENGINE LIGHT CODE YOU ARE GETTING.CODE SCAN AND TELL ME WHAT CODE YOU ARE GETTING.MOST VTECH ENGINE HAS PROBLEM WITH VTEC SOLENOID OR VTEC OIL PRESSURE SWITCH.MOST TIME CHECK THE OIL PRESSURE BY REMOVING VTEC OIL PRESSURE SWITCH FROM THE LOCK UP SOLENOID AND CONNECT AN ADAPTER BETWEEN THE SWITCH AND THE SOLENOID. BUT I CANT SAY ITS YOUR VTEC SYSTEM UNTIL YOU CODE SCAN CAR.OIL PRESSURE SHOULD BE 50 PSI @ 3000 RPM OR 85 PSI @3000 RPM.

CHECK VTEC SWITCH OIL PRESSURE.SHOULD BE 50 PSI @3000 RPM FOR THE S2000 OIL PRESSURE SHOULD BE 85 PSI @ 3000 RPM. IF OIL PRESSURE OKAY HAVE TO BE EITHER VTEC SWITCH FAULTY OR VTEC SOLENOID HAS FAILED.SOME TIMES PCM HAS FAILED TO THAT CONTROL CIRCUIT.

code 1259 is the actual v-tech code and oil pressure codes go from po520-po523. Many people do not have any idea what v-tech actually means. It's an actual oil solenoid valve that opens up above 4000 rpms and adds extra oiling to the cylinder head. To set this code po1259 you would have had your car above 4000 rpms for more than 3 seconds i believe and have this valve not work. Chances are that the valve it's self in the head is bad and setting this code. I have had it happen on a few other Honda's

If youe engine is stock - the VTECH should kick in at 5000-5500RPM.
Your car should be Dyno set. Every vehicle is different.

The 5000-5500 is good because if you were to set it down low it would almost be like having a non-vtec motor. If you set it at 6000, and your redline is 7000 then its not going to realy do anything. Again, almost like having a non-vtec motor.

PIC1
PIC2
PIC3

The first two pics are examples of where VTEC should be set earlier to smooth out the curve - the latter is an example of where VTEC should be set later to smooth the line out. You want the least noticeable transition from the non-VTEC to the VTEC lobes on your cam. That's when you'll make the most power at every point in the rev range.

Too early and your engine stumbles while it tries to get into the efficiency range of your big lobe- Too late and you have a huge jump where you could have had more power a few hundred rpm sooner.
The first graph had the VTEC set later (4400rpm) so that I wouldn't be jumping in and out of VTEC all the time on the highway, the second is the stock S2000 (6000rpm) that Honda sets so that the customer can feel the VTEC kick in (sells cars because it's cool, but isn't the best for max power), and the third was just set too early because it wasn't a custom tune.

Hopefully that gives you a more visual explanation of why you want to set your VTEC crossover point on a dyno.

Another suggestion is to unplug the IACV (Idle Air Control Valve) and see if the bog persists.

Finally - you may have a clogged cat. Remove the plug for the Throttle body Sensor and check again for the bog.

If no bog under this condition - your cat must be gutted, removed, or replaced.

Thanks!!

oil pump sounds like it maybe scavenging for oil ,check oil level, oilpressure----how long since filter was changed? youdoit

P2647 VTEC Oil Pressure Switch Circuit High Voltage - With Automatic Transmission Basicallly the sensor has gone bad or an oil passage has become blocked.

**. Locate the Variable Timing Electronic Control (VTEC) pressure switch on the end of the cylinder head. Honda has had problems with the VTEC oil pressure switch, there is an updated part number for the vehicle (37250-PNE-G01). On this vehicle the VTEC oil pressure switch can fail at any RPM.
2. The VTEC oil switch is normally closed, and grounds the reference voltage from the Engine Control Module (ECM) on the Blue/Black (BLU/BLK) wire. If the code sets at idle - 2500 RPM - and the Brown/Yellow wire has a good ground, then suspect a faulty VTEC oil pressure switch.
3. At approximately 2500-4000 RPM and when driving the vehicle, the VTEC system should turn on. To turn on the system, the ECM energizes the VTEC Solenoid valve and it allows oil pressure into the intake valve rocker arms, the oil pressure opens the VTEC oil pressure switch so the Engine Control Module (ECM) can verify that the VTEC did turn on correctly.
4. The code will set at idle to 2500 RPM if the reference voltage is not grounded. The code will set above 2500-4000 RPM if the VTEC oil switch does not open.
5. If the code sets at 2500-4000 RPM or higher, the problem can be a low oil level or pressure, or a malfunction in the VTEC assembly.
Potential Causes: Low Engine Oil
Plugged Oil Passage
Insufficient Oil Pressure
Plugged Oil Screen
Insufficient Oil Volume
Malfunctioning VTEC Oil Pressure Switch
Defective VTEC Solenoid

reset the ecu pull #6 fuse 15a for 10 msec. check oil level fill if needed. start engine hold at 3 grand for at least 2 sec road test if still comes back 1259 repeat 2 times. If it is gone it is intermit problem check for loose terminals at VTEC solenoid vavle oil pressure switch and the ECM/PCM. If you still have the code turn ignition off remove resonator disconnect the VTEC oil pressure switch 2p connector check for contnuity between VTEC oilpress switch terminals 1 and 2 if none replace the oil pressure switch. if yes measure voltage between ECM/PCM connector B9 and body ground. Voltage? repair open wire between B9 and the oil pressure switch. If no than the ECM/PCM will need to be checked for the latest software and reprogrammed to be further diaged. This will only be able to bedone at the dealer.

Please rate me solved...thanks!
DTC P1259: VTEC SYSTEM MALFUNCTION
1. Perform PCM reset procedure. See SELF-DIAGNOSTICS - INTRODUCTION article. Start engine
and run at 3000 RPM with no loads and transmission in Park or Neutral until radiator fan comes on. Road
test vehicle. Accelerate in 1st gear to an engine speed over 4000 RPM and hold that engine speed for at
least 2 seconds. If DTC P1259 is not indicated during first road test, repeat road test 2 more times. If DTC
P1259 is indicated, go to next step. If DTC P1259 is not indicated, problem is intermittent. System is
okay at this time. Check for poor connections or loose wires at VTEC solenoid valve connector and PCM.
See ENGINE PERFORMANCE WIRING DIAGRAMS article. Repair as necessary.
2. Turn ignition off. Disconnect VTEC pressure switch 2-pin connector. Check for continuity between
VTEC pressure switch terminals. If continuity exists, go to next step. If continuity does not exist, replace
VTEC pressure switch.
3. Turn ignition on. Measure voltage between ground and VTEC pressure switch harness connector terminal
No. 2 (Blue/Black wire). If about 12 volts exist, go to next step. If about 12 volts do not exist, check for
an open or short in Blue/Black wire between VTEC pressure switch and PCM 31-pin connector "C"
terminal No. 10. Repair as necessary. If wire is okay, substitute a known-good PCM and recheck. See
SUBSTITUTING PCM in SELF-DIAGNOSTICS - INTRODUCTION article. If symptom or problem
goes away, replace original PCM.
4. Measure voltage between VTEC pressure switch harness connector terminals. If battery voltage exists, go
to next step. If battery voltage does not exist, repair open in Brown/Black wire between VTEC pressure
switch and ground connector located on left side of engine, under throttle plate, between end of radiator
hose and cooling fan switch. See ENGINE PERFORMANCE WIRING DIAGRAMS article. If wire is
okay , substitute a known-good PCM and recheck. See SUBSTITUTING PCM in SELFDIAGNOSTICS
- INTRODUCTION article. If symptom or problem goes away, replace original PCM.
5. Turn ignition off. Disconnect VTEC solenoid valve connector. Measure resistance between ground and
VTEC solenoid valve connector. See ENGINE PERFORMANCE WIRING DIAGRAMS article. If
resistance is 14-30 ohms, go to next step. If resistance is not 14-30 ohms, replace VTEC solenoid valve.
6. Remove VTEC pressure switch and install Pressure Gauge Adaptor (07NAJ-P07010A) and A/T Low
Pressure Gauge (07406-0070300). Reinstall VTEC pressure switch into adaptor. Connect tachometer.
Start engine and with no loads and transmission in Park or Neutral until radiator fan comes on. Because
engine is running with no load, oil pressure must be checked within one minute. Check oil pressure at
engine speeds of 1000, 2000 and 3000 RPM. If oil pressure is less than 7 psi (48 kPa), go to next step. If
oil pressure is 7 psi (48 kPa) or more, check VTEC solenoid valve. See SYSTEM & COMPONENT
TESTING article.
7. Turn ignition off. Disconnect VTEC solenoid valve connector. Connect a fused jumper wire between
battery voltage and VTEC solenoid valve connector. Start engine and check oil pressure at 3000 RPM. If
oil pressure is more than 57 psi (393 kPa), go to next step. If oil pressure is 57 psi (393 kPa) or less,
check VTEC solenoid valve. See SYSTEM & COMPONENT TESTING article.
8. Ensure jumper wire is still connected to VTEC solenoid valve connector. Start engine and allow it to idle.
Set engine speed to more than 4000 RPM and measure voltage between ground and PCM 31-pin
connector "C" terminal No. 10 (Blue/Black wire). See ENGINE PERFORMANCE WIRING
DIAGRAMS article. If battery voltage exists, go to next step. If battery voltage does not exist, replace
VTEC pressure switch.
9. Turn ignition off and disconnect jumper wire. Check for continuity between VTEC solenoid valve
harness connector and PCM 25-pin connector "B" terminal No. 12 (Green/Yellow wire). See Fig. 2 . See
ENGINE PERFORMANCE WIRING DIAGRAMS article. If continuity exists, go to next step. If
continuity does not exist, repair open in Green/Yellow wire between VTEC solenoid valve connector and
PCM 25-pin connector "B" terminal No. 12.
10. Check for continuity between ground and VTEC solenoid valve connector. See ENGINE
PERFORMANCE WIRING DIAGRAMS article. If continuity exists, repair short in Green/Yellow
wire between VTEC solenoid valve connector and PCM 25-pin connector "B" terminal No. 12. If
continuity does not exist, substitute a known-good PCM and recheck. See SUBSTITUTING PCM in
SELF-DIAGNOSTICS - INTRODUCTION article. If symptom or problem goes away, replace original
PCM