P1284 Cylinder #8 High To Low Side Open

How to Fix P1284 Cylinder #8 High to Low Side Open


If you’re experiencing the P1284 error code on your vehicle, it means that there’s an issue with the cylinder #8 high to low side open. This can cause a variety of problems, including reduced engine performance and fuel efficiency. Fortunately, fixing this issue is relatively straightforward, and you can do it yourself with a few basic tools and some know-how.

Step-by-Step Guide

Step 1: Check the Wiring

The first thing you should do is check the wiring for any damage or corrosion. Start by locating the cylinder #8 injector and tracing the wiring back to the engine control module (ECM). Look for any frayed wires, loose connections, or signs of corrosion. If you find any issues, repair or replace the wiring as necessary.

Step 2: Check the Injector

If the wiring looks good, the next step is to check the injector itself. Start by disconnecting the electrical connector from the injector. Then, using a multimeter, check the resistance across the injector terminals. The resistance should be between 11 and 18 ohms. If it’s outside of this range, replace the injector.

Step 3: Check the Fuel Pressure

If the injector checks out, the next step is to check the fuel pressure. Start by connecting a fuel pressure gauge to the fuel rail. Then, turn the ignition on and check the pressure. It should be between 35 and 45 psi. If it’s outside of this range, there may be an issue with the fuel pump or fuel pressure regulator.

car vertical

Step 4: Check the ECM

If everything else checks out, the issue may be with the ECM itself. Start by checking the ECM for any signs of damage or corrosion. If everything looks good, try resetting the ECM by disconnecting the battery for a few minutes. If the issue persists, you may need to replace the ECM.

Useful Tips

– Always disconnect the battery before working on any electrical components.
– Use a multimeter to check for continuity and resistance.
– Refer to your vehicle’s service manual for specific instructions and torque specifications.


Fixing the P1284 error code is relatively straightforward, and with a little know-how, you can do it yourself. By following the steps outlined above, you can diagnose and fix the issue, restoring your vehicle’s performance and fuel efficiency.


1. Can I drive my vehicle with the P1284 error code?

While it’s technically possible to drive your vehicle with the P1284 error code, it’s not recommended. This issue can cause reduced engine performance and fuel efficiency, and it’s best to address it as soon as possible.

2. How much does it cost to fix the P1284 error code?

The cost of fixing the P1284 error code will depend on the specific issue causing the problem. In some cases, it may be as simple as repairing a damaged wire, while in others, it may require replacing an injector or the ECM. It’s best to consult with a mechanic or refer to your vehicle’s service manual for specific costs.

3. How can I prevent the P1284 error code from occurring?

The best way to prevent the P1284 error code from occurring is to perform regular maintenance on your vehicle. This includes changing the oil and filters, checking the spark plugs, and inspecting the wiring and electrical components. Additionally, avoiding harsh driving conditions and using high-quality fuel can also help prevent issues.