OBD2 Linking Error after dead battery

Maintenance/Repairs
1

HI.

2002 GMC Envoy battery died about a month ago. Replaced the battery, but the truck was running really rough. Used OBD2 reader to clear codes, cleaned throttle body, car runs fine now.

A few days ago the car wouldn’t start, wouldn’t turn over, no electrical power of any sort, and wouldn’t release the key. Got the key out, disconnected the positive battery cable, reconnected it, started no trouble.

Now the check engine light keeps flashing. So we hooked the reader up yesterday. THe code said “linking error.” We need to have our annual inspection soon, and it won’t pass with the check engine light on no matter what the reason for the light. So we need to figure this out.

How can I fix an OBD2 linking error?

2

OBD2-Connector-Pinout
OBD2-Connector-Pinout.png600×520 22.6 KB

Make sure your battery is healthy and all battery connectors and cables are clean and good. You should have 12 volts on bottom right pin. If not check fuses and wiring.

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3

If all is good with the wiring and the car won’t start and you still can’t connect… assume the ECU has died.

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4

Remove and clean the battery connectors and posts w/a battery tool, then check the basic battery/charging system operation with this test:

Before the first start of the day the battery should measure about 12.6volts. Immediately after starting the engine at idle it should measure 13.5-15.5 volts.