P1627

P1627 PCM/ECM A/D Conversion Error

System Description
Some of the components, such as the vehicle speed sensor, send the information along to the powertrain control module (PCM)/engine control module (ECM) in the form of analog data. The PCM/ECM must then convert the analog data to serial data in order to analyze it. The PCM/ECM continuously monitors this activity every 125 milliseconds and checks for active malfunction codes on inputs to the Analog/Digital Multiplex (A/C 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.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM/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.
- Both cooling fan turn on.

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

Step 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 PCM/ECM must be reprogrammed. Refer to the latest Techline procedure for PCM/ECM reprogramming.