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Lexus IS 300 P0354: Coil Pack “D” Malfunction – Diagnosis


P0354 Lexus IS 300

P0354 is a generic OBD2 code that indicates that the ignition coil “D” has a problem with the primary or secondary wiring circuits. If your Lexus IS 300 has released this code, it may be accompanied by P0304. P0354 is a relatively simple diagnosis and is usually caused by a bad coil pack or wiring harness problem, although it may be caused by other factors.

P0354 Ignition Coil “D” Primary/Secondary Circuit → Malfunction

Primary or secondary wiring?

It is important to determine whether it was the primary or secondary circuit that launched the code. Luckily, it’s easy to determine which is the culprit.


He primary It is the wiring harness that goes from the ECM/PCM of your IS 300 to the ignition system itself A shorted, open, or poorly grounded wiring harness is almost always what causes P0354 when it is the primary wiring side that has thrown the code.


He secondary the spark side of the equation. This means that the spark plugs, the spark plug wires (if so equipped), or the spark plug itself are causing your IS 300 to throw P0354. Ignition coil “D” indicates that the problem is in the fourth cylinder. You will have to look up which cylinder is number four in your engine. Different manufacturers use different methods. Here is a good explanation of how to locate the fourth cylinder.

There is a really easy test to determine if it is the primary or secondary wiring that is throwing this code on your IS 300. Move the ignition components (coil pack, spark plug wire, spark plug) from the D/4 cylinder to another and erase the codes. If the code “moves” from the fourth cylinder, you know it is a secondary problem. If it remains, it is a primary. We delve into this below (go straight there).

P0354 Symptoms: Lexus IS 300

Lexus IS 300 P0354 Diagnostics

  • check engine light– The check engine light may be the only thing you notice when you have this code, especially if it is caused by an intermittent wiring problem on your IS 300.
  • Misfires– P0354 may be accompanied by P0304. P0304 indicates a misfire in the fourth cylinder. If P0354 is resolved, P0304 will usually also be cleared. Misfires can cause a lack of power and/or engine hesitation. It can also damage the catalyst.
  • Sudden slowdown– Your vehicle may slow down if the fourth cylinder does not receive enough spark. You may also smell raw fuel while your IS 300’s engine is running.

P0354 Causes: Lexus IS 300

These are the most common problems that cause P0354:

  • Wiring problems (short circuit, open or poor ground connection)
  • Defective coil pack
  • Loose connection on the coil
  • defective PCM

P0354 Diagnosis

The first goal of diagnosing P0354 is to determine if it is a primary or secondary wiring problem on your IS 300. If you do that, you will have eliminated half the variables.

Voltage test (optional, but saves time)

The first place you would want to start looking for what could be causing P0354 on your IS 300 would be the wiring harness. You can use a digital voltmeter to check if the coil pack is receiving the proper signal. You should set it for A/C Hz and check if it is between 5-20hz

If it is between 5-20hz, it is very likely that the coil pack has gone bad. Although it could also be a bad spark plug or spark plug wire. If you have no signal, it’s time to look at the wiring harness. If you don’t have a voltmeter, you can use the parts swap method to help you determine if it is the primary or secondary side that is causing your problems. See directly below .

Parts exchange

A good way to determine if it is an ignition-related component and not a wiring problem is to reset the fault code and exchange the coil, spark plug, and spark plug wire (if equipped) with another one. cylinder. If the misfire “jumps” to the cylinder where you just changed the ignition components on your IS 300, then you know what you’re looking at is a coil, spark plug wire, or (most likely) fault. of the coil pack.

If the misfire moved the cylinders, you can go ahead and replace the spark plug, spark plug wire, and coil pack. If you’re on a tight budget, you can keep resetting the code and swap ignition parts one at a time until the misfire returns to cylinder 4. Start with the coil pack.

This method is only as difficult as the fourth cylinder.


If the misfire didn’t move from the fourth cylinder, then you know you most likely have a problem with the wiring harness that runs from the coil pack to the IS 300’s PCM/ECM. Look at where the wiring harness connects. to the coil pack. Is it damaged or loose in relation to the other cylinder connections? If so, it may need to be changed.

If the misfire is intermittent, shake the wiring harness and see if it affects engine operation. If it starts or stops crashing, you’ll know you’ve found the problem. Look anywhere the harness bends or touches something sharp. See if it looks burned anywhere. Check for damage and repair the wiring accordingly.

Make sure it has solid ground.


If you still can’t find the problem, it’s time to take a look at the PCM. This is the least likely answer and an area where it may be time to call in the professionals.

Ending: P0354 Lexus IS 300

P0354 is usually fairly easy to diagnose using the swap test, even if you don’t have any specialized diagnostic tools. If there is anything you can add, leave a comment below. Good luck repairing your IS 300!


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