Code 24

[turbo_tuna]

Hi All,

I am working on getting my Syclone sorted out after a complete tune up and turbo overhaul. I am still chasing the poor idle and occasional stalling, however when I took it out for a test drive I got a code 24. After searching I found the following:

CODE 24 VEHICLE SPEED SENSOR (VSS) CIRCUIT 4.3L TURBO (VIN Z)
SYCLONE AND TYPHOON (PORT)
Circuit Description: The ECM applies and monitors 12 volts on CKT 437. CKT
437 connects to the DRAC, which alternately grounds CKT 437, when receiving
voltage pulses from Vehicle Speed Sensor (VSS) when drive wheels are turning.
This pulsing action takes place about 2000 times per mile and the ECM will
calculate vehicle speed based on the time between “pulses.” A “Scan” tool
reading should closely match the speedometer reading with drive wheels turning.

So what does this really mean? Where is the VSS (in the transmission?) and what is the DRAC. I also have an ABS indicator light. I suspect this may be related. If the vehicle has been sitting is it possible that dirt is interfering with the sensors?

Regards,
WS

 

[mattw]

Re: Code 24

The speed sensor is in the transfer case. The DRAC is the white plastic box attached to the ECM. The DRAC reads the signal from the VSS and turns into the proper PPM(Pulse Per Mile) reading that the ECM is looking for. There are different DRACs for different wheel size/axle ratio combos..

I doubt you have dirt in the VSS but its easy enough to pull and check. Not sure what they cost but I'd probably start by replacing that..

 

[turbo_tuna]

Re: Code 24

Thank you for your response. I will replace it and post my results.

 

[DaveP]

Re: Code 24

Does the Speedometer work? If = YES, the only thing it can be is a bad connection in the dk brown wire at the DRAC or the ECM.

If = NO, check the BRAKE fuse first. It powers the DRAC. If = OK, post back, we'll go from there.

 

[turbo_tuna]

Re: Code 24

Speedometer works. To make matters more interesting, I just took it out and noticed the check engine light is no longer on. I did not disconnect the battery or attempt to clear the codes.

Does the Speedometer work? If = YES, the only thing it can be is a bad connection in the dk brown wire at the DRAC or the ECM.

If = NO, check the BRAKE fuse first. It powers the DRAC. If = OK, post back, we'll go from there.

 

[DaveP]

Re: Code 24

It's a false Code 24 then. There are ways to set 24 while testing. A mis-adjusted switch assy on the shifter (Park-Neutral) can contribute to false 24's.

Clear it and forget about it.

 

[turbo_tuna]

Re: Code 24

Thank you for the assist. I took it out again and the code 24 did not come back. Now I am onto the ABS light and poor idle.

It's a false Code 24 then. There are ways to set 24 while testing. A mis-adjusted switch assy on the shifter (Park-Neutral) can contribute to false 24's.

Clear it and forget about it.