ryanmax

just got my dmm but I am not really sure how to use some of the funcitons...did a good search and read quite a bit of info but most is geared toward the electrical engineer who already knows a lot about ohms and the like. I know where the ks is and unplugged the connectors (91 se )but how do i exactly test it? the stuff i read says measure between terminals a and b and check for continuity (there should be continuity) is this the same as measuring resistance (the ohmeter function)?? If it is the same, then am I correct that continuity means the multimeter will read zero? (if there is a number then my ks is bad) also, I am assuming I need to have ignition off and disconnect battery (the directions with multimeter that are also useless to a layman says that to measure resistance the thing to be measured must be taken out of the circuit) final question is which connector do I measure, the one coming from the ks under the exhaust manifold or the one that goes into the ecu? Or both? Thanks in advance, because this electrical testing is a little confusing.

internetautomar

iTrader: (30)

the knock sensor should read approx. 500k ohms.
that measurement is taken between the 2 terminals of the sensor

Wiking

- FSM speaks of continuity, still 500k is typical. And continuity is from 0 ohms until no reading =no continuity. lol. All this means that manual writer is at loss =no cont between ears.
- Yes, resistance measurement is in question
- Batt can be connected, ign off
- KS is in the engine, its resistance is of interest - if any
- Nissan guys are the confuzeus followers, so youre the straight guy...

After measurement, FIY, this is all rubbish: the KS may still be bad, does not depend what reading u get.

The only sure way is to test drive using a 500kohm bypass resistor (use high octane fuel). Note: Nissan tester might be able to test KS, during drive, dunno. VG: http://www.cardomain.com/memberpage/748507/9

The KS piezo element is the 10c toy doll buzzer installed into metal housing, pre-tensioned. (I suppose the tension dies during aging as a piezo does then give no resistance.)

Bypass R installed (on ECU side) VGE!:

Tarzan

I almost agree, but one part: the KS is more likely an element from a $1 BBQ lighter...

eric93SE

iTrader: (1)

realize that the measurement taken is supposed to be taken DIRECTLY from the sensor, this does not include the sub harness. If you measure both terminals from the subharness you will get no continuity since one terminal does not go to the sensor it only acts as RF sheilding. So you have to measure from one terminal at the subharness to ground (one terminal will give no reading and one will).

Wiking

Good point, VE:

VG has two terminals down to the KS, measurable, may be bypassed as illustrated.
VE is like u say; can be measured between gnd and one terminal (not shield) ...and the resistor also has to be set between gnd and one terminal.

(Btw, piezo price is under ten cents when purchased in Nissan quantities...)

ryanmax

I am obviously not an expert at electrical testing (never used a dmm before but want to learn) so I am still a little confused. Let me see if I have this right:
batt connected, ignition off, unplug sensor and place two probes between the two terminals of the connector closest to the actual knock sensor (or the connector closest to the ecu?) and measure resistance between the two termnials, which should be 500k ohms. If it is anything very different from 500k ohms it is bad (although Wiking says that measurements don't mean all that much, could be bad/good regardless)

Next questions, maybe a dumb one, but I always use 87 octane, don't remember reading in my manual that premium was necessary, but do you think my ks could be funcitoning correctly and that it is actually sensing detonation from the low octane fuel?

what I will try to do is test my sensor, fill up with premium and run that down to half a tank, and then if that doesn't help, try the bypass to see if that improves. only thing I'm worried about is running the car a long time with the bypass - can this really blow up your engine, or will you be fine as long as you ALWAYS use 91? thanks in advance.

ryanmax

thought of something else, what do you mean "taken directly from the sensor"? I also am confused about the subharness....tia

Wiking

First define the engine type u have: VE or VGE. Look my website for VGE.
Note: VGE is different from VE; VE has higher compression.

Repeat: sensor is in the engine. Its resistance should be measured, NOT ECU. No need to take KS for measurement: use the opened plug pins.

KS may be good or bad; hmm. real wisdom... I suppose 87 should be ok; still fouled engine may do pre-ignite.

I've been using bypass resistor one? year, will never repair the stupid KS... I use 95 octane only [might even be equal to US 91?].

Too advanced ignition can always blow an engine, so its better to know what are u doing. (KS is automatic ign adjuster sensor; ECU takes care if it detects ping from this sensor. If sensor fails, ECU retards ign and then u will lose at the pump &pwr). Without KS, user has to keep ignition conditions favourable as has been the case for last 100 years of automotive history...

DIY the test, or go to Nissan and ask for this KS test only with Nissan Consult -device; ask for that price only: I suppose it cannot be too bad...