GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2005 🢒 TopKick C-Series (Conventional) C6/C7/C8 🢒 Engine 🢒 Engine Electrical 🢒 DTC P0512

Circuit Description

When the Ignition is placed in the start position, 12 volts is supplied to the ECM notifying it that crank has been requested. If the ECM detects voltage on the circuit with the engine running, the DTC will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0512 Start Switch Circuit

Conditions for Running
    • Battery voltage is between 10-16 volts.
    • Key switch is "ON".
    • Engine speed is more than 1000 RPM.

Conditions for Setting the DTC

Starter switch continues "ON".

Action Taken When the DTC Sets

The ECM will illuminate the malfunction indicator lamp (MIL) the first time the fault is detected.

Conditions for Clearing the MIL/DTC

DTC P0512 can be cleared by using the Clear Info option on the Tech 2 or by using the Diag Clear Switch.

Diagnostic Aids

Inspect for the following conditions:

    • Poor connections at the ECM--Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connections.
    • The relay remains applied on idling during cold start.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Electrical Connector End Views

1

Is DTC P0512 set when the ignition is ON or when the engine is operating?

--

Go to Step 2

Go to Diagnostic Aids

2
  1. Start the engine and allow it to idle for 30 seconds.
  2. Measure the voltage between the clutch/start switch circuit of the engine control module (ECM) and ground.

Does the voltage measure equal to the specified value?

12 V

Go to Step 3

Go to Step 4

3
  1. Inspect the wire harness and/or starter switch for a short to ground or faulty switch.
  2. Repair or replace the wire harness or starter switch as necessary. Refer to Wiring Repairs .

Did you complete the action?

--

Go to Step 4

--

4
  1. Clear the DTCs.
  2. Replace the ECM assembly. Refer to Engine Control Module Replacement/Restore Fuel Rate Data .

Does DTC P0512 reset?

--

Go to Step 2

System OK