should my engine light come on if the knock sensor is disconected.

 

Yes.

The ECM runs a knock sensor test routine to verify ESC circuit operation. Leaving the knock sensor (part of the ESC system) unconnected, or if the sensor is actually Bad, will cause this test to fail, and the SES light to be turned on. I Think this will also store a code 43, but don't quote me on that...

 

And it will store a 43.

 

my knock sensor is disconected and the engine light is not on and seems to run fine. i was wondering if light should be on i drove it around the block 2 times

 

Since no one answered.
Could it be that your SES light is broken?
Try this, unplug the TPS sensor and see if the light comes up.
Should give a 22 code.
If no code, I would definately check the bulb in the DIC.

 

I looked at your profile. It looks like you've got an '85. That version of ESC does not have any hardware/electrical diagnostic capability. IIRC, it was later years when software was added to perform a test (by advancing the timing and looking for knock) to see if the system was functional. Unfortunately, if the test was performed under conditions of high humidity or high octane fuel usage, the engine wouldn't knock, and the software would mistakenly think the system had failed. Later ESC units (around '90 or so, I can't recall) actually measured for electrical DC continuity to the sensor, and even later units monitored the AC signal from the sensor.

 

Incorrect. Per my '85 FSM, the diagnostic chart for code 43, "This system also performs a functional check once per start up to check the ESC system. To perform this test the ECM will advance the spark when coolant is above 90 deg C. and at wide open throttle (WOT). The ECM then checks the signal at B7 to see if a knock is detected. The functional check is performed once per start up and if knock is detected when coolant is below 90 deg C. (194 deg F.) the test has passed. If the functional check fails the "check engine" light will remain on until the ignition is turned off or until a knock signal is detected."

Note the contradiction in temperatures. That's word for word out of the FSM. Also - one of the switches that can be edited in the PROM program is the Knock Diagnostic on/off.

 

No contradiction in the temperatures. The software assumes that when the coolant is above 90C temperature, the engine parts are at operating temperatures and clearances, and any significant noise picked up by the sensor is true knock, signifying that the system is operating correctly. Below 90C coolant, the software assumes that the pistons are still "cold', and there is frequently excess piston to wall clearance in that situation. This excess clearance will cause piston slap noise of significant amplitude to be picked up by the knock sensor. This mechanical noise signal will electrically trigger the ESC hardware, and the ECM software will read this signal, confirming that the system is working.
As I mentioned above, this software diagnostic system was frequently fooled by engines that did not exhibit piston slap noise when cold, or were driven in humid climates that suppressed WOT detonation. Without either of these noise events happening, the software would frequently be fooled into thinking that the system had a failure or disconnection. Hence the move to actual electrical tests, versus software tests, in the later versions of the ESC electronics.

 

No argument - we are on the same page, just looking at it from different perspectives.

The "issue" I have with the software diagnostic on the '85 (as an M.E. I tend to blur the line between Software diagnostics and Hardware diagnostics and lump it all together based on Function - us M.E. guys are like that...) is that the enable temperature of 90 C. (194 F.) never happens for guys like me running the motor cooler (nominally) than that.

I run mine at about 185 F, for example, and therefore the ESC diagnostic never takes place. Not to mention it happens only during the first (after startup) trip to WOT, which Also nearly never happens, at least for Me driving the car.

BTW - 69427 - where in Florida are you, anyhow. If you don't mind my asking. I spent four years living in Cocoa Beach (stationed at Patrick) and then another 9 years in St. Pete, myself. College at USF. Moved back to the northeast after graduation, and it's been a lot of years since. Still make an annual trip down for speedweek, and to see friends in the St. Pete area. Tickets are bought for the 2009 trip

 

Orlando area. Drop me a PM if you're in town. We'll have an adult beverage and talk cars.

 

The knock Diagnostic threshold temp and the knock Control threshold temps are not the same. The Control threshold temp is editable in the PROM program anyhow (I have mine beginning knock control at 40 deg C or about 105 deg F.), while the Diagnostic temp is not. At least not with any of the editor masks I've seen. ( I have both Tunerpro and CATS tuner to play with)

Been too long since I learned assembly language to try and wade through the code now for myself, at least not until I bump up against something more aggravating That I think needs fixing, and isn't accessible using the available masks..

There is the nagging MAF airflow code setpoint issue, but that's a whole 'nother problem

That PROM code is only a 4K file, afterall. How bad can it be