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Author Topic: NSS/Clutch Pedal Switch Code 67 Troubleshooting  (Read 10132 times)
El Hombre
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« on: March 19, 2011, 06:10:10 pm »

NSS/Clutch Pedal Switch Code 67 Troubleshooting

Codes Definitions:

67 - Park Neutral Position Switch Circuit Open; A/C On -Manual (O), Manual Lever Position Sensor Out Of Range/A/C On (CM,O), Clutch Switch Circuit Failure (CM)

Clutch Pedal Switch, T5 Transmission Gear Switch & Auto Trans. Neutral Switc

Background Information and Previous Misconceptions

The neutral safety circuit for manual tranny setups, is comprised by two switches, clutch sense switch and a gear/neutral safety switch on the tranny, setup in a parallel circuit as shown below. The clutch sense switch is open pedal up, and the gear switch is open in any gear other than neutral. None of these switches is used in the starting circuit to activate the starter, they simply "inform" the ECM of the position of the clutch pedal or gear selector. if you look at the clutch pedal switch assy. above, you'll notice it is a dual switch type, one is used for the ECM and the other is used in the starting circuit.

On automatic transmissions, the neutral switch is also used as the 12-vdc activation voltage gate for the starter solenoid. It will not allow the start 12-vdc voltage to reach the starter solenoid, unless transmission speed selector is positioned in P or N. Different to the setup for manual transmissions, 12-vdc during start-ups will be present to the ECM as well, as shown in the two ECM and starter circuit diagrams below.

  • Engine idle control. The EEC uses the NSS circuit to control idle strategy to be used by the EEC. If the system is not able to ID a "in-neutral" condition, idle surging and rolling will occur.
  • NSS input is also an engine load determiner along with other inputs (TPS, MAF, VSS, etc).
  • Having a code 67 logged in the system can cause engine stalls in configurations with a manual transmission.
  • Its cruise control use has not changed.
  • Since NSS input is used to determine idle control strategy, its importance in the system is real. The presence of a code 67 failure will not allow the EEC to run the KOER self test for "saftey reasons.
  • If you still are hesitant to understand its importance for idle control, suggest you take a look at the documented video clip at http://sbftech.com/index.php/topic,7333.0.html .

Tools Required: (in addition to the generic tools)

  • Digital VOM or DMM
  • Wiring diagrams for your year Mustang
  • Vacuum diagram for your year Mustang

Testing Procedure:

1. If a code 67 is registered during KOEO, make sure transmission is in neutral and A/C is off...repeat KOEO self-test and check for code 67 to be registered....YES?..goto 2....NO?...code was caused by "operator error".

2. Make sure transmission is in neutral, A/C off, press clutch pedal and re-run a KOEO while maintaining the clutch pedal to the floor, check for code 67 to be registered....YES?...goto 3...NO?...need to check connection and wiring of gear switch at transmission....if OK...gear switch requires to be replaced.

3. This is where it gets uncomfortable.....check the clutch pedal switch under the dash board, identify the conector with the Lt. Blue/Yellow and Black/White wires and disconnect it. Install a jumper wire between the connector pins, and rerun a KOEO self-test...check for code 67 to be registered.....YES?...goto 4....NO?....replace pedal switch assembly.

4. Disconnect ECM, measure continuity from pin 30 to Lt. Blue/Yellow wire pin at the clutch switch, resistance should be less/equal to 5 ohms....YES?...goto 5.....NO?....pin 30 wire needs to be traced and repaired for an open.

5. ECM and pedal switch disconnected, measure continuity from Black/White wire pin at the pedal switch to pin 46 at the ECM connector resistance should be less/equal to 5 ohms....YES?...goto 6.....NO?....pin 46 wire needs to be traced and repaired for an open.

6. At this stage of the pinpoint, the only circuit left for testing is the A/C Clutch Signal (ACCS) at pin 10 in the ECM....ECM disconnected, Ign On, checke pin 10 voltage output to ground...voltage should be less than 1.0 vdc.....NO?...service short to power in ACCS wire.....YES?....ECM needs to be replaced.

Hope this helps someone....



'86 Mustang GT, X-303 cam, Holley DP 700, RG Tran., 289 Heads   Ford Smilie 2

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