If your 1990 Honda Accord’s check engine light is on, you might be wondering what the problem is. What does Code 43 mean on a 1990 Honda Accord? This specific trouble code points directly to an issue with your car’s fuel supply system, and it’s a common one for vehicles of this era. Don’t worry, though—it’s often something you can diagnose and sometimes even fix yourself with a little guidance.
What Does Code 43 Mean On A 1990 Honda Accord
In simple terms, Code 43 is your car’s computer telling you it has detected a problem with the fuel supply system. More specifically, it means the Powertrain Control Module (PCM) is not seeing the correct signal from the Fuel Supply System circuit. On your 1990 Accord, this almost always relates to the fuel pump or its control circuit. The computer monitors voltage in this circuit, and when it’s out of the expected range, it stores Code 43 and illuminates the check engine light.
Symptoms of a Code 43
You’ll likely notice more than just a glowing dashboard light. The symptoms are related to fuel delivery, so they affect how the engine runs. Here are the most common signs:
- Check Engine Light: The primary indicator, of course.
- Hard Starting or No Start: The engine may crank but not fire, or it might take several tries to start.
- Engine Stalling: The car might start but then die shortly after, especially at idle.
- Poor Performance: Lack of power, hesitation, or stumbling during acceleration.
- Rough Idle: The engine may shake or feel unstable when stopped.
Common Causes of Code 43 in Your 1990 Accord
Several components can trigger this code. It’s helpful to think of them in order from simplest to most complex to check. Here’s a breakdown of the usual suspects:
- Faulty Fuel Pump: This is the most frequent culprit. The pump may be weak, failing intermittently, or have stopped working entirely.
- Bad Fuel Pump Relay: The relay acts as a switch for the fuel pump. A failed relay will cut power to the pump.
- Blown Fuel Pump Fuse: A simple but critical check. Locate the fuse box and inspect the fuel pump fuse.
- Wiring or Connector Issues: Corrosion, breaks, or loose connections in the wiring harness to the fuel pump or relay can cause this code.
- Problematic Main Relay: Often called the “PGM-FI Main Relay,” this part powers the fuel pump and the car’s computer. It’s a known failure point on older Hondas.
- Failed Fuel Pressure Regulator: While less common, a regulator that can’t maintain proper pressure can confuse the system.
- Failing PCM: This is very rare, but a malfunctioning computer itself could theoretically set the code incorrectly.
How to Diagnose Code 43: A Step-by-Step Guide
Safety first! Always work in a well-ventilated area, have a fire extinguisher nearby, and disconnect the battery’s negative terminal before working on electrical components. Let’s walk through the diagnostic process logically.
Step 1: Preliminary Checks
Start with the easiest possibilities. Listen for a humming sound from the rear of the car when you first turn the key to the “ON” position (but don’t start the engine). You should hear the fuel pump prime for about two seconds. If you hear nothing, it points to a power issue (fuse, relay) or a dead pump.
Step 2: Check the Fuse
- Locate the under-hood fuse/relay box.
- Find the fuse for the fuel pump (consult your owner’s manual for the exact location).
- Visually inspect the metal strip inside the fuse. If it’s broken or melted, replace it with one of the same amperage.
Step 3: Test the Fuel Pump Relay
The relay is also in the under-hood box. You can often feel or hear a faint click when the key is turned on if it’s working. A better test is to swap it with another identical relay in the box (like the horn or A/C relay). If the problem goes away, you’ve found the issue.
Step 4: Inspect the Main Relay
This relay is usually located under the dashboard, near the steering column. It’s a notorious source of problems. Symptoms of a bad main relay include the car dying when warm or failing to start. You can sometimes resolder the joints inside a faulty main relay, but replacement is often the best long-term fix.
Step 5: Check for Power at the Fuel Pump
This requires a multimeter. You’ll need to access the electrical connector at the fuel pump, which is under the rear seat or in the trunk area on the 1990 Accord.
- Disconnect the fuel pump connector.
- With the key turned to “ON,” use the multimeter to check for 12 volts at the harness connector (refer to a wiring diagram for the correct pins).
- If you have power here, the fuel pump itself is likely bad. If you have no power, the problem is in the wiring or relays between the pump and the battery.
Step 6: Test the Fuel Pump Itself
If you had power in Step 5, you can perform a direct test. Carefully apply 12 volts directly from the battery to the pump’s terminals (not the car’s harness). Use jumper wires with alligator clips. If the pump doesn’t run, it’s definitively failed. Be extremely cautious, as this involves fuel vapors.
How to Fix the Problem
Once you’ve identified the faulty component, the repair can begin. Here are the common fixes:
Replacing the Fuel Pump
This is a moderately difficult job. You’ll need to depressurize the fuel system, disconnect the battery, and drop the fuel tank or access the pump through an interior panel. Always use a new pump seal/gasket to prevent leaks. It’s a good idea to replace the fuel filter at the same time.
Replacing Relays
Both the fuel pump relay and the main relay are plug-and-play components. Simply unplug the old one and plug in the new. For the main relay, you may need to contort a bit under the dash, but it’s generally straightforward.
Repairing Wiring
If you found damaged wires, you’ll need to cut out the bad section and splice in new wire of the same gauge. Use proper crimp connectors and seal them with heat-shrink tubing to protect against moisture and corrosion. Electrical tape alone is not a reliable long-term fix in a car’s environment.
Clearing Code 43
After making the repair, you need to clear the code to turn off the check engine light. On your 1990 Accord, you can do this by disconnecting the negative battery terminal for about 5-10 minutes. This resets the PCM. Reconnect the battery, start the car, and let it idle for a few minutes. If the repair was successful, the check engine light should stay off. If it comes back, the underlying issue wasn’t fully resolved.
Preventative Maintenance Tips
To avoid future fuel system issues, consider these tips:
- Keep your fuel tank at least a quarter full. Running on empty causes the fuel pump to overheat, shortening its life.
- Replace your fuel filter according to the maintenance schedule (usually every 30,000 miles). A clogged filter makes the pump work harder.
- Use a quality fuel injector cleaner every few thousand miles to keep the entire system clean.
- Address electrical gremlins like corroded connectors as soon as you notice them to prevent wider issues.
FAQ Section
Can I drive my Accord with a Code 43?
It is not recommended. The car may stall without warning, which could be dangerous in traffic. The problem could also leave you completely stranded. It’s best to diagnose and fix it as soon as possible.
How much does it cost to fix Code 43?
Costs vary widely. If it’s just a relay or fuse, you might spend $20-$50. A professional fuel pump replacement, including parts and labor, can range from $500 to $800 or more. Doing it yourself can cut the cost to just the part, which is typically $100-$250 for a quality pump.
Is Code 43 always the fuel pump?
No, but it’s the most common cause. Always check the relays, fuses, and wiring first before condemning the pump. These checks are cheaper and easier and can save you money and time.
What’s the difference between the fuel pump relay and the main relay?
The fuel pump relay controls power specifically to the fuel pump. The main relay (PGM-FI) provides power to the fuel pump relay, the fuel injectors, and the car’s computer. A bad main relay can cause multiple problems, including Code 43.
Could a bad battery cause Code 43?
It’s unlikely to be the direct cause, but a weak battery or poor battery connections can cause low voltage issues that might confuse the PCM. Always ensure your battery and charging system are in good health when chasing electrical trouble codes.
Dealing with a Code 43 on your 1990 Honda Accord can feel daunting, but it’s a very systematic problem. By starting with the simple checks—fuses and relays—you can often find the issue without needing complex tools. Remember, this code is almost always related to power getting to the fuel pump. With patience and careful diagnosis, you can get your reliable Accord back on the road running smoothly again. The key is to not overlook the simple solutions before moving on to the bigger jobs like pump replacement.