P1627

DTC P1627 ECM A/D Conversion Error

System Description
Some of the components, such as the vehicle speed sensor, send the information along to the engine control module (ECM) in the form of analog data. The ECM must then convert the analog data to serial data in order to analyze it. The ECM continuously monitors this activity every 125 milliseconds and checks for active malfunction codes on inputs to the A/D multiplex (MUX) that are shorted high. This Diagnostic Trouble Code (DTC) will set when an active malfunction is present that affects the A/D MUX diagnostic.

Conditions for setting the DTC
- Ignition ON.
- Active malfunction present that affect A/D MUX diagnostic.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will not illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Steps 1 - 4:

Test Description
The number(s) below refer to step(s) on the diagnostic table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
4. The replacement ECM must be reprogrammed. Refer to Powertrain Control Module / Service and Repair.