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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
Teh information i'm goin to gve you is for a honda 1999 accord dx sedan, the code means a problem with the vtec solenoid valve,
you might have to replace the vtec soleoind switch or have it diagnose for one of our technichians listed here on fixya
just go to homepage and look for a repair man by typing your zip code
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