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Old 08-12-2019, 08:49 PM   #1
jpsuli
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Join Date: Aug 2015
Location: Minneapolis
Posts: 179
 

1997 SL2
Default Running cluster outside of car - mileage stuck?

Hello,

I have a 99 cluster that I want to run outside of the car, I found this:
Quote:
Originally Posted by OldNuc View Post
5000pulses/mile from the PCM. Below from FSM.

SPEEDOMETER/ODOMETER
The speedometer receives vehicle speed information from the Powertrain Control Module (PCM ). The vehicle speed signal is passed through an RC filter to the input of the speedometer/odometer driver Integrated Circuit (IC ), located in the instrument panel cluster. The high-to-low edge of the square wave input triggers the IC to provide a well defined pulse of current to the coil of the speedometer gage. The IC also counts the input transitions and uses this information to drive the odometers. The vehicle completes one mile for every 5000 pulses received from the PCM.

There are two odometers in the instrument panel cluster. The odometer shows total mileage since the vehicle was built and cannot be reset. The trip odometer which shows total mileage since last reset, and can be reset to zero at any time. The two odometers are not synchronized. This means that even through one of the odometers may advance by a mile/kilometer the other one may or may not advance to the next mile/kilometer at the same time. The odometer is back lit by a single bulb to make it easier to read in all lighting conditions.

TACHOMETER
The tachometer is directly controlled by the powertrain control module (PCM) using a Pulse Width Modulated (PWM ) signal based on the signal received from the Crankshaft Position (CKP ) sensor. The PWM signal to the cluster is passed through an RC filter and sent to the tachometer driver integrated circuit (IC). The high-to-low edge of the PWM signal triggers the IC to provide a well defined pulse of current to the coil of the tachometer. The engine completes one revolution for every six pulses received from the PCM. The PCM monitors circuit 121 for an open, short to ground or short to voltage and will set DTC P1693 if certain parameters are met.
I grabbed a PWM switch and found the two wires that control ignition and the speedo, I was able to get it to work somewhat unreliably though the mileage does not move.

Any thought to get the mileage to work? I have spare PCMs to make it work, will try to play with it this weekend.
Attached Images
File Type: jpg speedo.jpg (122.5 KB, 11 views)

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