Code 31

CIRCUIT DESCRIPTION
The ignition module sends a signal to the TCM that indicates engine speed (RPM). The Engine Control Module (ECM) also receives this signal. When the vehicle is in neutral gear and the engine is at idle, the engine speed should be approximately 800 rpm.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
1. Tech-1 displays engine speed signal received at terminal 11 or 55 of TCM connector.
2. Tachometer displays engine speed signal.
3. Ignition control module output fault may exist.

DIAGNOSTIC AIDS
Trouble Code 31 sets when the TCM detects no engine rpm signal at terminal 11 or 55 with the throttle open greater than 12 percent and the vehicle speed greater than 19 mph (30 km/h).

CIRCUIT DIAGRAM

Engine Speed Signal Circuit:

CODE 31 DIAGNOSTIC CHART

Code 31 Diagnostic Chart: