Toyota Knock Sensor

What to look for in knock sensor failure

First off there are few things that you need to consider when diagnosing and replacing a knock sensor on Toyota vehicles.

  • Some Toyota models have two knock sensors(left bank and right bank)
  • It’s not un-common to have knock sensor wire failure
  • The knock sensors are usually priced at or above $100.00 each, even if purchased aftermarket.
  • There are two types of sensor brands used on Toyota vehicles
    1. Matsushita
    2. Nippondenso
  • Highly labor intensive to access the knock sensors for replacement.

Nippon Denso Knock Sensor

Matsushita Knock Sensor

So, there are some things to consider when replacing the knock sensor. Doesn’t matter if you perform this yourself or have a repair shop do the repair. These things should still be considered.

When replacing the knock sensors the upper and lower intake manifold has to be removed and that alone is a lot of work. If the vehicle has dual sensors (one on each bank) you may want to consider replacing both of them while the intake manifold is removed. There is also a knock sensor wire that is common to have problems due to the intense heat under the intake manifold. The wire is fairly inexpensive at a cost of around $50.00 from the dealer and I always recommend to replace it regardless. Usually the insulation is hard and cracked and if it’s ok at the time of removal, there is a good chance that it won’t be after it has been disturbed. At the least the connector breaks where it connects to the sensor.

Other things to consider during knock sensor replacement on your Toyota

Since we know that the intake manifolds need to be removed, what other items have to be serviced while the intake is removed?

Valve cover gaskets
At the mileage your vehicle is at when knock sensor failure usually occurs is around the same time you start seeing the valve cover gaskets starting to leak
Spark plugs
The same goes with the spark plugs, and if they’re not due yet they will be due soon. If you’re model year has ignition wires you may want to consider replacing them also.
Coolant crossover hose
Underneath the lower intake manifold there is a coolant crossover hose. Toyota does make very good hoses, but think about the amount of time before that intake will ever be removed again? Hopefully never, replace the crossover hose. It’s pretty inexpensive anyways.
Coolant passage cover plate
After removing the lower intake, if you look in the galley way there you will see a plate. That plate seals a coolant passage and eventually will start to leak. If not leaking yet you may start to see coolant tracking or corrosion build up. This just means that it is leaking, but not at this time. At first it will only leak under certain temperatures, due to expansion and contraction of metal at the different temperatures.

Know that all that has been covered, you may be thinking this all adds up to be an expensive repair. How important is this really? Well, I will explain to you what a knock sensor does, but before I do that you may want to know that depending on the state you live in a failed knock sensor will result in a failed DEQ slip. Depending on the model I have also seen them cause automatic transmissions to loose overdrive. The computer does not want to command overdrive when this sensor has failed. This has stumped me before, especially when you get a customer that already knows about the check engine lite. The customer is also well aware of the cost to repair this and says, “Don’t worry about the check engine lite, I’m only concerned about why my transmission doesn’t have overdrive”. If you have not run into this before it can stump you pretty good.

What does a knock sensor do?

Knock sensors prevent predetenation. Up to a point, more power can be produced in an engine by increasing spark advance. But too much advance causes pre-detonation. Pre-detonation is also called knock, detonation and spark knock, pinging or pinking. Once knock starts, performance decreases and there is a risk of serious engine damage. Knock gets its name because it causes vibrations and banging in the cylinder. Mild knock causes a “pinging” noise that sounds like marbles or small ball
bearings bouncing on a piece of metal. Severe knock sounds like someone banging on a door. Mild knock reduces power, wastes fuel and increases emissions. Severe knock can destroy internal engine parts including the pistons, connecting rods, exhaust valves, head gaskets and spark plugs. The knock sensor detects these situations and prevents them from happening. So you can see why it’s important, it can save the life of your engine.

What causes spark knock or detonation?

  1. Detonation occurs when the air-fuel mixture doesn’t burn smoothly or ignites too soon.
  2. Detonation can be caused by “hot spots” in the cylinder, such as carbon deposits or spark plugs that are too hot for the engine.
  3. Detonation also occurs from excessive combustion chamber temperatures.
  4. Last but not least detonation will occur if spark timing is advanced too far or low fuel octane.

Other things to consider if your thinking you still don’t need the knock sensor.

When a computer detects a failed knock sensor it will default the ignition timing back 5 degrees or more to prevent spark knock. This will result in loss of gas mileage and also rob your vehicle of power. Especially in today’s vehicles, ignition timing (and mechanical cam timing) is one of the most important factors as to how we get so much power out of such a small engine. So, if you’re thinking your not concerned about replacing the knock sensor because you don’t hear any type of detonation in your engine. The reason for this is the good old fail-safe mode of computer-controlled engines. You most likely won’t even be aware of the fail-safe mode until you get the problem fixed and now notice an increase in power and fuel economy!

This post was written by: Martin Hand

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Martin Hand

About Martin Hand

ASE Certified L1 Advanced Mastertech. Martin Hand has over 15 years experience in Asian and European Import Auto Repair. Specializing in electrical diagnosis, engine performance, AT/MT transmission repair/rebuild. Martin is also pursuing a degree in Computers Science & Information Systems starting at Portland Community College while he plans to transfer to OIT. Certified in Java application level programming, experienced with other languages such as PHP, Ruby, JavaScript and Swift. Martin has future plans of automotive diagnostic software development.

74 Comments

  • Teddy Klaus says:

    98 v6 Camry: If and when I remove the intake manifold to replace knock sensors (and harness – thanks), do I automatically replace the gasket?

  • sergio says:

    1996 4runner, 3.4 5vzfe, 4wd automatic. I need to replace the knock sensor and I am ready to order it online but cannot find the knock sensor wire, coolant crossover hose under the manifold or the coolant passage plate anywhere online. Help?

  • Haroon says:

    What is the difference between denso and mitsubishi knock sensor and how would i know which one is fitted in my car??

    • Martin Hand Martin Hand says:

      I don’t what the differences are but I think they have different electrical connectors and ohm ratings. The dealer may be able to tell you buy the vin number. Probably different between US and Japan built models. If the first vin character is J then it’s Japan built.

  • Munkh-erdene Chimedtseren says:

    hi. my english is not good. sorry
    my car is toyota hilux surf 3.4l /5vzfe engine/ 2003
    it is indicated check engine, after fuel pump is changed new one, /error p0328/
    also, while accelerating / about 4000 rpm/ engine is backfiring.
    I changed the knock sensor, the light turned on again with the same code
    please help

    • Martin Hand Martin Hand says:

      A failed knock sensor will not cause severe engine performance problems as your explaining. There has to be something else causing the backfire. Check fuel trim for lean conditions or incorrect cam timing. Knock sensor will only default ignition timing retard 5°-10°.

  • Ulinda says:

    I have an 02 toyota Bb that recently the check engine light came on. Apparently my knock sensor needs to change. I’m musty not sure which modal best fits my car because I notice there is now than one type.

  • John Anthony says:

    Thanks for the time you obviously spent on this site make up.
    I’ve got a ’94 LandCruiser 1FZ with 280k. I do have some valve seal leakage too. My symptoms are similar to your descriptions which lead me to think faulty KS. I can even manipulate the severity / rapidness of the knock by feathering the gas ever so slightly while in motion . My engine throws no codes though, even when I’ll I have no forward propulsion for x amount of time. Usually within 3 miles of startup..after a few minutes I am able to proceed as usual.
    Any thoughts on No Code? My CEL indicator does indeed come on during initial turn up. I have not circuit tested the KS…my thoughts are after 20+yrs, maybe it’s time?

    (New OEM erg, modulator, fuel pump resistor, fuel pump,wire loom, dizzy,fuel filter,TPS,throttle cable,fuel press regulator)

    • Martin Hand Martin Hand says:

      Sounds like the engine is having pre-detonation problems(pinging). Sometimes the knock sensor will not overcome severe pinging but you have to monitor it with a scanner to be sure. Monitor knock sensor signal and ignition timing to verify ECM is responding to the knock signal. You can duplicate pinging by tapping next to knock sensor with hammer and punch or long large flathead screwdriver.

  • Manny Ramirez says:

    i replace snocks sensor 1 and 2 the wire to, and send same code. p0330 is 2001 toyota hilinder 3.0.

    • Martin Hand Martin Hand says:

      Where did you order knock sensors from? There are two different types (Nippon Denso or Mitsubishi) hopefully you installed the correct ones. Not sure if the electrical connectors are interchangeable or not. If parts are ordered from Toyota dealer then they’re probably correct. Also continuity check circuits from sensors to PCM.

  • tash says:

    Hi. I replaced the knock sensor on my twincam 4age engine bt I still get same code.while travelling the light comes on n vehicle looses power.wat else can I replace in order to eliminate my problem.

    • Martin Hand Martin Hand says:

      Something else must be causing your problem. A failed knock sensor will only retard ignition timing about 5 degrees. This would not cause a significant power loose just minor noticeable difference and loose of gas mileage.

  • conner says:

    I have an 2007 5.7L tundra. My check engine light is on and the code shows that it is my knock censor, but I don’t hear any knock. My question is, sometimes when I get above 70mph my transmission won’t drop to 5th gear and will run right above 3000rpm instead of dropping down close to 2000rpm. I have also noticed that it only happens in the 4th-5th gear change and it only really happens when my check engine light is on. Is this caused by the knock censors?

    • Martin Hand Martin Hand says:

      Very possible. The knock sensor error will need to be diagnosed and repaired regardless so I would start there. This will also effect gas mileage and engine power.

  • mike says:

    1996 4runner sr5 3.4. won’t shift to overdrive. changed solenoids, coolant temp sensor and thermostat. so far no luck. when changed solenoids, fixed for a minute but went back to not working

    • Martin Hand Martin Hand says:

      If the overdrive started to work after replacing solenoids then your on the right track just something was overlooked unless you have a bad solenoid again. Check all electrical connections for broken or loose pin terminal and/or melted connectors.

  • Kevin Gainer says:

    91 V6 Camry. (OBD Code 52): Oscilloscope shows knock sensor “response” if I tap on the manifold BUT only a volt or two in amplitude (but maybe I am knocking too far from sensor? So 1 or 2 volts seems “low”? I guess wire is OK because I do get a reading on scope? If wire “broken” I would guess I would get nothing? Code 52 only set after I re-installed engine (I did not touch sensor though…not unscrewed)…never had problem or any codes ever in 26 years. Circuit back to ECM seems: leaving ECM plugged in gives about 3k ohms which I think is simply a resistor in ECM so I think circuit is intact. Maybe there is “resistance” on signal wire (pigtail)??? There is continuity, otherwise nothing would appear on scope. I hate to take apart not understanding exactly what the failure is. No apparent loss of engine power by the way…on a 91 must not be much change in fail safe mode???? Pigtail discontinued by the way..so I guess I have to make.

    • Kevin Gainer says:

      Follow-up…actually, it might not even be a volt…i had set scope to millivolts to get anything to read so maybe too much resistance on wire? I guess no way to test wire without taking it apart to get to OTHER end of wire.

    • Martin Hand Martin Hand says:

      Continuity check the circuit from sensor to ECM connector (3 ohms is too high). Needs to be less that .5 ohm typically 0.1 ohm or less.

      • Kevin Gainer says:

        thanks…I’ll try that. The knock sensor must make almost no difference by the way as implemented in that early year (1991) because the car runs flawlessly with Code 52…feels like a v-8 engine. I guess could be some degradation to MPG though (I haven’t checked..just guessing).

  • Anonymous says:

    I replaced both my knock sensors and wire on my 3.4 l 96 Toyota 4 Runner and still have knock sensor code.

    • Martin Hand Martin Hand says:

      Perform a continuity check from the ECM to the knock sensor then ohm check the circuit, if everything checks good then suspect ECM failure. NOTE: ECM failure is very un-common

  • Sunny says:

    I changed the knock sensor on my 1989 Toyota pickup 3.0 and now the light turned on again with the same code and also now my truck lacks
    on power … Wat can I do to fix? Plz help I’m car less and can’t go to work

    • Martin Hand Martin Hand says:

      Need to replace the knock sensor wire also, the one that goes under the intake to the sensor. You can try ohm testing the circuit from the ECM. Single wire circuit, ground shielded signal wire.

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