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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 54 (Engine Controls And Fuel - 2.8L (LWN) Diesel - Diagnostic Information And Procedures (2 Of 3)) >> Diagnostic Information and Procedures >> DTC P16D7-P16D9 >> Component Testing

Component Testing

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.

Relay Test

  1. Ignition/Vehicle - Off
  2. Remove the component: KR121A Reductant Control Module Relay 1 & KR121B Reductant Control Module Relay 2
  3. Test for 70 to 110 ohms between the test points:
    • KR121A Reductant Control Module Relay 1 - Component terminal 85/6 & 86/4
    • KR121B Reductant Control Module Relay 2 - Component terminal 85/20 & 86/22
    • If not between 70 and 110 ohms 

      Replace the component: KR121A Reductant Control Module Relay 1 or KR121B Reductant Control Module Relay 2

    • Go to next step: If between 70 and 110 ohms 
  4. Test for infinite resistance between the test points:

    KR121A Reductant Control Module Relay 1

    • Component terminal 30/B+ & 85/6
    • Component terminal 30/B+ & 86/4
    • Component terminal 30/B+ & 87/5
    • Component terminal 85/6 & 87/5

    KR121B Reductant Control Module Relay 2

    • Component terminal 30/21 & 85/20
    • Component terminal 30/21 & 86/22
    • Component terminal 30/21 & 87/B+
    • Component terminal 85/20 & 87/B+
    • If less than infinite resistance 

      Replace the component: KR121A Reductant Control Module Relay 1 or KR121B Reductant Control Module Relay 2

    • Go to next step: If infinite resistance 
  5. Connect a 3 A fused jumper wire between the test points:
    • KR121A Reductant Control Module Relay 1 - Component terminal 86/4 & 12 V
    • KR121B Reductant Control Module Relay 2 - Component terminal 86/22 & 12 V
  6. Connect a jumper wire between the test points:
    • KR121A Reductant Control Module Relay 1 - Component terminal 85/6 & Ground
    • KR121B Reductant Control Module Relay 2 - Component terminal 85/20 & Ground
  7. Test for less than 2 ohms between the test points:
    • KR121A Reductant Control Module Relay 1 - Component terminal 30/B+ & 87/5
    • KR121B Reductant Control Module Relay 2 - Component terminal 30/21 & 87/B+
    • If 2 ohms or greater 

      Replace the component: KR121A Reductant Control Module Relay 1 or KR121B Reductant Control Module Relay 2

    • Go to next step: If less than 2 ohms 
  8. All OK.
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