DTC P1259: A Problem In The VTEC Oil Pressure Switch Circuit Or VTEC Solenoid Valve Circuit: Notes

Special Tools Required

Pressure gauge adapter 07NAJ-P07010A
A/T low pressure gauge w/panel 07406-0070300
A/T pressure hose, 2,210 mm 07MAJ-PY4011A
A/T pressure adapter 07MAJ-PY40120

Do the powertrain control module (PCM) reset procedure (see HOW TO RESET THE PCM ).
Start the engine.
Warm up the engine to normal operating temperature (cooling fan comes on).
Road test the vehicle: Accelerate in 1st gear to an engine speed over 4,000 rpm. Hold that engine speed for at least 2 seconds. If DTC P1259 is not repeated during the first road test, repeat this test two more times.
Is DTC P1259 indicated?
1. YES - Go to step 5.
2. NO - Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the VTEC solenoid valve and PCM.
Turn the ignition switch OFF.
Disconnect the VTEC oil pressure switch 2P connector.
Check for continuity on the VTEC oil pressure switch between the pressure switch 2P connector terminals No. 1 and No. 2.

Fig 1: Checking Continuity On The VTEC Oil Pressure Switch Between Pressure Switch 2P Connector Terminals No. 1 & No. 2
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Go to step 8.
2. NO - Replace the VTEC oil pressure switch.
Turn the ignition switch ON (II).
Measure the voltage between the VTEC oil pressure switch harness 2P connector No. 1 terminal and body ground.

Fig 2: Measuring Voltage Between VTEC Oil Pressure Switch Harness 2P Connector No. 1 Terminal & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Go to step 10.
2. NO - Inspect for an open or short to ground in the wire between the VTEC oil pressure switch and the PCM connector terminal C10 (1999-2000, 2002-2004 models) or A20 (2001 model). If the wire is OK, substitute a known-good PCM and recheck (see HOW TO SUBSTITUTE THE PCM FOR TESTING PURPOSE ).
Measure voltage across the VTEC oil pressure switch harness 2P connector.

Fig 3: Measuring Voltage Across VTEC Oil Pressure Switch Harness 2P Connector
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage?
1. YES - Go to step 11.
2. NO - Repair open in the wire between the VTEC oil pressure switch and G101.
Turn the ignition switch OFF.
Disconnect the VTEC solenoid valve IP connector.
Check for continuity on the VTEC solenoid valve between the solenoid valve 1P connector terminal and body ground.

Fig 4: Checking Continuity On VTEC Solenoid Valve Between Solenoid Valve 1P Connector Terminal & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there 14-30 Ω?
1. YES - Go to step 14.
2. NO - Replace the VTEC solenoid valve.
Remove the VTEC oil pressure switch (A). Install the special tools as shown, then reinstall the VTEC oil pressure switch.

Fig 5: Removing VTEC Oil Pressure Switch
Courtesy of AMERICAN HONDA MOTOR CO., INC.
Reconnect the VTEC solenoid valve 1P connector and VTEC oil pressure switch 2P connector.
Connect a tachometer.
Warm up the engine to normal operating temperature (cooling fan comes on).
Check oil pressure at engine speeds of 1,000, 2,000 and 3,000 rpm. Keep measuring time as short as possible because the engine is running with no load (less than 1 minute).
Is pressure below 49 kPa (0.5 kgf/Cm ² , 7 psi)?
1. YES - Go to step 19.
2. NO - Inspect the VTEC solenoid valve (see VTEC Solenoid Valve Test ).
Turn the ignition switch OFF.
Disconnect the VTEC solenoid valve 1P connector.
Attach the battery positive terminal to the VTEC solenoid valve terminal.
Start the engine and check oil pressure at an engine speed of 3,000 rpm.
Is pressure above 390 kPa (4.0 kgf/Cm ² , 57 psi)?
1. YES - Go to step 23.
2. NO - Inspect the VTEC solenoid valve (see VTEC Solenoid Valve Test ).
With the battery positive terminal still connected to the VTEC solenoid valve, measure voltage between PCM connector terminal C10 (1999-2000, 2002-2004 models) or A20 (2001 model) and body ground.

Fig 6: Measure Voltage Between PCM Connector Terminal C10 & Body Ground (1999-2000 Models)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 7: Measure Voltage Between PCM Connector Terminal A20 & Body Ground (2001 Model)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 8: Measure Voltage Between PCM Connector Terminal C10 & Body Ground (2002-2004 Models)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there battery voltage above 4,000 rpm?
1. YES - Go to step 24.
2. NO - Replace the VTEC oil pressure switch.
Turn the ignition switch OFF.
Disconnect the battery positive terminal from the VTEC solenoid valve terminal.
Check for continuity between the VTEC solenoid valve harness 1P connector terminal and PCM connector terminal B12 (1999-2000, 2002-2004 models) or B2 (2001 model).

Fig 9: Checking Continuity Between VTEC Solenoid Valve Harness 1P Connector Terminal & PCM Connector Terminal B12 (1999-2000 Models)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 10: Checking Continuity Between VTEC Solenoid Valve Harness 1P Connector Terminal & PCM Connector Terminal B2 (2001 Model)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 11: Checking Continuity Between VTEC Solenoid Valve Harness 1P Connector Terminal & PCM Connector Terminal B12 (2002-2004 Models)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Go to step 27.
2. NO - Repair an open in the wire between the PCM connector terminal B12 (1999-2000, 2002-2004 models) or B2 (2001 model) and VTEC solenoid valve connector.
Check for continuity between the VTEC solenoid valve 1P connector terminal and body ground.

Fig 12: Checking Continuity Between VTEC Solenoid Valve 1P Connector Terminal & Body Ground
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Repair a short in the wire between the PCM connector terminal B12 (1999-2000, 2002-2004 models) or B2 (2001 model) and VTEC solenoid valve connector.
2. NO - Substitute a known-good PCM and recheck (see HOW TO SUBSTITUTE THE PCM FOR TESTING PURPOSE ). If symptom/indication goes away, replace the original PCM (see HOW TO RESET THE PCM ).