Knock sensor to ECU resistance

[turboAWDfanatic]

Searched, couldn't find an answer for this...

I've had horrible PK problems that are very random. After trying all the usual PK fixes, a fellow DSM owner recommended checking for continuity between the KS and the ECU to see if there's too much resistance. Well, my meter reads 1.2 Mohms resistance between the KS plug and pin 9 on the ECU.

Question is, should there be little to no resistance? Should I run a new wire from the KS to the ECU? In this thread, it was mentioned that you should run a shielded wire from the KS to the ECU. Is this to avoid electrical noise interference or heat?

Thanks!

 

[slowgsr]

is that 1.2 mili, or mega? There is a very large difference.

However, yes you should have a shielded wire grounded at the ECU end only.. only ever ground one end or you could create a ground loop and current could potentially flow blah blah blah.. anyways. The shielding is to reduce noise, not heat.. Heat effects resistance, but on the amount of current that flows though the wiring for a knock sensor which is almost nothing it will have absolutley no effect at all in readings..

A copper wire that isn't an excessive distance (250+ft) usually has a resistance of about 0.2-0.3 ohms.

I do not know the exact circuitry for the knock sensor on these cars, but im assuming the knock sensor creates a voltage which travels to the ecu, and goes though a current limiting resistor which the ecu reads the voltage drop across.. The knock sensor probably creates voltage though pizo electric.

The wire from the knock sensor (UNPLUGGED ONLY), to the pin on the ecu harness.. (UNPLUGGED ONLY), should be 0.2-0.3ohms assuming theres no inline resistors or any type of 'added' resistance in that circuit. You will have much different readings if your probing the wire checking resistance when its connected to the ems and plugged into the knock sensor.

Perhaps replace the sensor or ensure its in good working order, than go from there.

EDIT: From what I remember over the winter the wire for the knock sensor is already shielded from factory on the 90's, atleast it was on my stock harness.

 

[turboAWDfanatic]

Thanks for the help!

It was MEGA ohms. =( I first tested for continuity (no buzzing sound from my multi-meter). kept bumping it up, 200ohm, 1Kohm, 1Mohm before I got a decent reading. I measured with the wire unplugged from the ECU. I tapped into the end of the plug on the harness in the engine bay, and to pin 9 on the ECU harness. I pose the original question just to be sure that there are no resistors like you mentioned. Is it SUPPOSED to be nominal resistance like .1-.2 ohms, or is it supposed to register a specific resistance above that?

I have replaced the sensor, so I assume that a brand new factory Mitsubishi KS is good, but I suppose I could test it somehow to be sure.

You mention having the wire grounded at the ECU. I was planning on plugging the knock sensor into the factory plug, but snipping the positive wire and replacing it, while still using the factory ground wire which grounds at the ECU. I suppose I should test that as well. Anybody know what pin the KS is grounded to? Is it one of the sensor grounds on the same plug as the main KS wire (17 and 24)?

As for the replacement wire, is there any particular kind I should look for...or is it just as simple as looking for "shielded wire" in whatever gauge I want?