Hard Trouble Code E24: Notes

NOTE: If this code is not displayed during second pass of diagnostic codes, it is an intermittent failure and cannot be diagnosed using this procedure.

The speed sensor generates an electrical signal representing vehicle speed, and the vehicle speed sensor buffer amplifies and inverts this signal for ECM.

Trouble code indicates that speed signal is not being received by ECM when vehicle is in 4th gear. This can be observed on engine data parameter P.1.2. as reading of 0 MPH while driving. Possible causes are: Defective speed sensor, defective vehicle speed sensor buffer (buffer amplifier), defective wiring, terminals, etc., or ECM unable to process speed signal.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

To begin diagnosis, determine if speedometer is operating properly. If not, repair speedometer assembly.
If speedometer is operating properly, determine if speed signal is being received by ECM. This can be observed by noting vehicle speed sensor reading (parameter P.1.2) with drive wheels turning. If parameter P.1.2 indicates actual MPH, malfunction is not present at this time.
With parameter P.1.2 indicating 0 MPH, and drive wheels turning, back probe vehicle speed sensor buffer pin F with voltmeter to ground. If voltage is 6.5 volts or greater, check for faulty vehicle speed sensor buffer connector or faulty speed sensor buffer. If voltage present is 5-6.5 volts, check for a faulty ECM connector or faulty ECM.
If voltage at pin F is below 5 volts, disconnect 8-way vehicle speed sensor buffer connector and measure voltage from pin F to ground. If voltage is below 5 volts, check for an open or short to ground in circuit No. 437. If wiring is okay, check for faulty ECM connector or faulty ECM. If voltage on pin F is greater than 5 volts, replace vehicle speed sensor buffer.