DTC 642

Possible Causes

• •5Vext is overloaded with too many sensors or faulty sensor
• •Faulty ECM
• •Faulty ECM (5Vref power supply)
• •Faulty MAP sensor
• •Faulty TIP sensor
• •Faulty harness (5Vref1 and 5Vrtn1 connections)
• •Intermittent Problem
• •Intermittent problem
• •Poor connection at sensor
• •Spread pins (caused by inserting probe or object into terminals)
• •Wire connected to terminal # 19 at the ECM is partially or completely shorted to ground

Suggested Actions

1. 1Check 5Vref1 and 5Vrtn1 connections
2. 2Jumper the MAP circuit to Vref (5 VDC) in connector on harness and check if DST displays MAP voltage of 4.7 VDC or greater
3. 3Jumper the TIP circuit to Vref (5 VDC) in connector on harness
4. 4Measure the voltage potential across 5Vref1 and 5Vrtn1 at connector using a DMM
5. 5Perform the On-Board (OBD) System Check
6. 6Troubleshoot DTC 642 or 643 first
7. 7Troubleshoot DTC 642 or DTC 643 first if present
8. 8Turn key off, disconnect wire harness header from ECM, carefully remove yellow lock from header at device output terminal, and check resistance between MAP input at ECM header and signal at device (do not insert probe into terminals to avoid spread pins)
9. 9Use Diagnostic Service Tool (DST) to check if 5Vext1 FB (VE5a_FB_raw) * 11/10 < 0.10 VDC
10. 10Use a DMM to measure the voltage potential across 5ref1 and 5V rtn1 at connector
11. 11Verify if DTC 642 displays with Key ON, Engine Running, and System Mode set to 'Running'

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