Diagnostic Aids

Perform this test only when directed by QUICK TEST. This test is intended to diagnose only the following circuits or systems:

• Neutral-Drive Switch (NDS)
• ECA
• Harness Circuits CES, CIS, NDS, NGS And SIG RTN

Fig 1: Neutral Drive Input Circuit

1. 1) Code 67/522, 525, 527, 528 Or 634 System Identification  Code 67/522, 525, 527, 528 or 634 is result of voltage being high at pin No. 10 (A/C input) or pin No. 30 (neutral drive) while cranking engine or during KOEO SELF-TEST. Possible causes of faults include A/C Circuit Shorted To Power, Neutral-Drive Switch Open, Faulty ECA or Starter Relay Disconnected During Self-Test.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 1) to step 8). No test procedures have been omitted.
2. 8) Check Neutral Drive Input  Turn ignition off and wait 10 seconds. Ensure heater control is in OFF position (if equipped). Ensure transmission is in Neutral or Park position. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, or loose wires; repair if necessary. Install breakout box, and connect ECA to breakout box. Set DVOM to 20-volt scale. With KOEO, measure voltage between test pin No. 30 and chassis ground. If voltage is greater than one volt, go to next step. If voltage is less than one volt, check A/C input signal to ECA, and service short to power in A/C input circuit. If vehicle does not have A/C, replace ECA. Remove breakout box and rerun QUICK TEST  .
3. 9) Check Neutral Drive Switch  Turn ignition off and wait 10 seconds. Install breakout box, leaving ECA disconnected. Set DVOM to 200-ohm scale. Disconnect vehicle harness from neutral drive switch and measure resistance across switch. If resistance is less than 5 ohms, repair open circuit in vehicle harness neutral-drive circuit. Remove breakout box, reconnect all components and rerun QUICK TEST  . If resistance is greater than 5 ohms, replace neutral-drive switch. Remove breakout box, reconnect all components, and rerun QUICK TEST.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 9) to step 12). No test procedures have been omitted.
4. 12) Check NDS Circuit For Short To Ground Or Closed Neutral Drive Switch  Turn ignition off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires; repair if necessary. Install breakout box, and leave ECA disconnected. Set DVOM to 200-k/ohm scale. Place transmission in DRIVE position. Measure resistance between test pins No. 30 and 40/60. If resistance is greater than 10 k/ohms, NDS circuit okay. Diagnose other possible causes. If resistance is less than 10 k/ohms, repair closed neutral drive switch or short circuit. Remove breakout box, reconnect all components, and rerun QUICK TEST  .