Code p1259 how do you fix code p1259

Hi there:
There is actually an old service news about this very code. there are two things that could be at fault but you will have to check a few things that are outlined in the article before knowing which parts need replacing... please read carefully below...

MIL with DTC P1259 - Vtec System Malfunction

On 1998 Accord L4s with VTEC, DTC P1259 (VTEC system malfunction) can set at idle or above 4,000 rpm:

If it sets at idle, the problem is with the VTEC pressure switch circuit (switch, connectors, or wiring).
If it sets above 4,000 rpm, the cause is low oil pressure in the VTEC system.

To find and correct the cause of the DTC, do this:
1. Use the PGM Tester to check the vehicle's freeze data or snapshot data to see when the DTC was set.
If it set at idle, go to step 2.
If it set above 4,000 rpm, go to step 4.

2. Disconnect the 2P VTEC pressure switch connector, and jump its two wires.

3. With the ignition switch ON (II), the PGM Tester should show that the VTEC pressure switch is ON.
If the Tester says the switch is ON, the wiring and connectors are OK, so the switch must be bad.
Replace the switch, clear the DTC, and return the vehicle to the customer.
If the switch is OFF, check for an open circuit between the switch and the ECM/PCM or between the switch and ground. After you repair the open circuit, recheck the switch, then clear the DTC, and return the vehicle to the customer.

4. Remove the valve cover, and check for a loose center head bolt on the intake manifold side. A loose bolt can cause a drop in pressure in the VTEC system.

If the bolt isn't loose, go to step 5.
If the bolt is loose, torque it to 22 lb-ft (29 Nm), turn it another 1/4 turn, and then turn it another 1/4 turn. If the bolt won't tighten, its threads are probably stripped.

5. Remove the VTEC rocker arms, and inspect them for sticking or missing synchronizer pistons or other valve train problems that could cause an oil leak.

If you find any piston or valve train problems, replace the faulty parts. Then clear the DTC, and return the vehicle to the customer.
If the pistons and the valve train are OK, do the DTC P1259 troubleshooting procedure on pages 6-7 thru 6-9 of the '98-99 Accord S/M.


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