Anyone know how the oil life monitor works?

[MadMikeyL]

I got an 89 XR7 a few weeks ago. I changed the oil in the car, and reset the monitor at the same time, and in about 1000 miles of driving, it was saying change oil now. Does anyone know generally how the monitor works, and also does anyone else have the same problem with it saying the oil needs to be changed way before it actually does? Thanks.

Mike

[68COUGAR]

Description

The Vehicle maintenance monitor (VMM) warns the driver of low oil, low radiator coolant, low fuel and low washer fluid conditions and indicates when to change engine oil. The system consists of an electronic module with a display, a coolant level sensor, a washer fluid level sensor, a combination oil level and temperature sensor, a fuel sender, a tachometer and a rheostat.

The module lights all segments of the display for 1 second, blinks them for 1 second, and then goes to normal operation whenever the ignition key switches to the RUN position. The oil change display turns off after 15 minutes if the engine is not running. This alerts the user that the VMM module is not getting a tachometer signal. The module is loacted in the top center of the instrument panel, directly above the radio.



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Low Oil Indication

The low oil warning lights when engine oil is 1.5 quarts low. The low oil level condition is determined by a combination of oil level readings made when the ignition key is turned OFF and ON. The Chart below shows the oil level indication based on the four different combinations of readings.

When the key is turned to the OFF position, oil level is sensed continuously until the readings is at normal level or until five minutes has elapsed. This is to prevent a false low reading during oil drain back.



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Low Fuel Indication

The low fuel indicator lights after the fuel level reaches approximately one-eighth of tank capacity, for 60 seconds. It lights within 15 seconds if the fuel is low when the ignition is first turned on. The low fuel condition is detected using input from the fuel sender. At one-eighth tank capacity and with a battery voltage of 13.5 volts to the VMM, the fuel sender outputs a voltage of 3.4 volts to the VMM. The VMM will light its warning indicator for any input voltages less than 3.4 volts. The VMM will not allow the warning indicator to turn off until the fuel sender outputs a steady voltage of 4.0 volts or above. This prevents fuel slosh from turning the warning indicator on and off.
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Low Radiator Coolant Indication

The low radiator coolant indicator lights after the coolant drops below the cold full line on the overflow bottle for 60 seconds as checked by a conductivity sensor. The low radiator indicator lights within 15 seconds if the coolant is low when the ignition is first turned on. The sensor ouptut is open when fluid level is normal and goes to ground when fluid level is low.
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Low Washer Fluid Indication

The low washer fluid indicator lights after the fluid reaches approximately one-third bottle capacity for 60 seconds. It lights within 15 seconds if the washer fluid is low when the ignition is first turned on. At low level condition, a float-type switch closes to battery voltage. The VMM turns on the warning indicator whenever a constant battery voltage is sensed at the input.
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Oil Change Indication

The green bar under OK on the oil change display is lit for 0% - 89% of the oil change cycle, the world SOON under the word CHANGE is lit for 90% - 99%, the word NOW is lit for 100% - 115%, the word NOW is lit and flashes every 18 minutes for 17 seconds after 115% of the oil change cycle.

The oil change display will turn off after 15 minutes if the VMM receives no tachometer signal. This is a diagnostic precaution that could be caused by an intermittent connection or by the engine not being on.

The VMM monitors engine oil temperature and engine tachometer signals to measure quality of oil and indicate when engine oil should be changed.
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Diagnosis & Testing

The VMM has a self-diagnostics test built into the module that can be performed with the module in the vehicle and the engine running. This test determines whether the module is getting and processing the signals necessary to function correctly. The self-diagnosis test should be used together with the Diagnosis Index and the pinpoint tests. Refer to the Diagnosis Index to determine which Pinpoint Test to perform. The Pinpoint Tests will refer to the self-diagnosis test for specific faults. Refer to system diagram and component pinout illustrations while performing diagnosis.
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Self-Diagnostics Test

The module has a self-test mode that can be entered while the module is in the vehicle. This mode will test the modules's response to engine rpm, oil temperature, fluid levels, and engine and electronic instrument cluster (EIC) wireing harness strap inputs.

Enter the test by starting the vehicle and within 16 seconds from engine start, pressing the reset switch and holding continuously for 4 seconds. The entire display will flash when the reset switch is pressed (if only the oil change display flashes, release the reset switch and see below). If the reset switch is released within 4 seconds, the dislpaly will stop flashing and normal operation will continue. Do not run engine faster than 6100 rpms.

If only the oil change display flashes in the above sequence, then the tach input signal to the module is missing. The Self Diagnostics Test cannot be entered until this signal is provided.

Each reset switch press and release advances the module to the next test. Turn the ignition OFF to terminate the self doagnostics test.
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Tach Input Test

As soon as diagnostics is entered the module is in the tach input test mode and the display lights up segments OK, CHANGE, NOW, SOON and GREEN BAR in sequence, proportional to the number of tach pulses measured (engine rpm). The faster the engine rpm, the faster the sequence lights.
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Oil Temperature Test

When the Reset switch is pressed and released, the display advances to this test. The "OIL" nomenclature is lit and oil temperature will be indicated per the table below.


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Fluid Level Tests

In fluid level test mode, LOW's are turned ON for a "low" reading and OFF for normal readings. The fuel ISO is also turned ON for low fuel. The oil change display stays OFF. When in the self diagnostics test mode, the fluid level indicators will respond instantaneoulsy, except for oil level which has up to an 8 second delay. See the Low Oil Indication section for an explanation of how oil level works.
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Engine Strap and EIC Sense Input Test

This test mode indicates which cluster and engine the VMM is sensing as determined by the wiring harness. See the connector drawing for the numbers of the pins used to do this.

The line on each side of "CHANGE" turns on to indicate that the module is in this test. The oil "LOW" turns on to indicate supercharged engine and off to indicate non-supercharged engine. The washer fluid "LOW" turns on to indicate electronic instrument cluster and off to indicate mechanical instrument cluster.
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Remaining Tests

The remaining self diagnostic tests are for engineering evaluation only. Turn engine OFF to exit self diagnostics test mode.







68COUGAR

[Mike Puckett]

My VMM trips every 1000 miles on both of mine too. Just change the oil on the 3rd or 4th reset.

[rickbtbird]

Originally Posted by Mike Puckett

My VMM trips every 1000 miles on both of mine too. Just change the oil on the 3rd or 4th reset.

Mine too and the oil low light on mine come on when the system is 1/2 quart low.

[90blkbrd]

I believe I have read that when the mileage for the oil change is that short means that the oil temperature sending unit in the oil pan isn't functioning correctly.

[Jogi]

68COUGAR, wow, that was a informative reply, straight to the bookmarks

[DutchSCFan76]

yeah 68Cougar, thats some usable sh@t you have there where did you get this info anyway?

Never thought the VMM had acutally more functions then monitoring 4 fluid levels

[68COUGAR]

Originally Posted by DutchSCFan76

where did you get this info anyway?

Straight outa the '89 Shop Manual. The first thing I did after buying my car (1989) is to order all the manuals (that were avail.) for it. They have been invaluable ever since.

68COUGAR

[Sweet90SC]

Had the same deal on my 90...changed it every 3rd reset...no biggie

[Jogi]

Is shop manual still available (other than Ebay..) if not, mayby someone should leak it in the net for common good

[The_Ghost]

Is a shop manual worth an aluminum spare?

[68COUGAR]

Originally Posted by Jogi

Is shop manual still available (other than Ebay..) if not, mayby someone should leak it in the net for common good

You could start with the Helm, Inc. website: www.helminc.com

This link should get you to the Thunderbird section faster: http://www.helminc.com/helm/search_s...Q0DSCJ5SET0290

I'd buy another shop manual, if I could get it on CD. Then I'd use the book in the shop, & the CD on the computer.

Currently the '89 Shop manual is OUT OF STOCK.....................But Helms will notify you when it's IN STOCK again, If you get on the WAITING LIST. If everybody who wants an out of stock manual, gets on the waiting list, it might encourage Helm to print the out of stock manuals!!!

68COUGAR

[thirdbird]

Originally Posted by 68COUGAR

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The module lights all segments of the display for 1 second, blinks them for 1 second, and then goes to normal operation whenever the ignition key switches to the RUN position. The oil change display turns off after 15 minutes if the engine is not running. This alerts the user that the VMM module is not getting a tachometer signal.

Hey 68,
If it lites up while key is in run with engine off, then goes out when key in run w/engine running, does that also mean cam sensor?
I have had mine out because the left side was always out and I thought it was just broken.

paul

[Kurt K]

I tried searching for it and couldn't find it, but somebody posted a link to the patent for the VMM a while back. I printed it out, but of course I can't find that right now either.

[BlackbirdSc94]

what if everything stays lit and the indicator always says now, I changed the oil last week, coolant levels fine and I dunno about the fuel since my needle reads off center (havnt let it go below half a tank for fear of getting stranded) I dont know about when the fuel light should come on IF it works