7A1–112 AUTOMATIC TRANSMISSION (4L30-E)
DIAGNOSTIC TROUBLE CODE (DTC) 51
ENGINE COOLANT SWITCH SHORT TO GROUND, PLUS OR OPEN
This DTC does NOT flash the CHECK TRANS
indicator and does NOT set the BACKUP MODE.
Circuit Description:
•
The Engine Coolant Temperature is measured by
a sensor in the coolant system. This information
is used by the Engine Control Module (ECM) for
the engine. The ECM provides the information:
Engine Warm to the Transmission Control
Module (TCM) when the ECM measures a
temperature higher than 70°C (158°F).
•
The information is provided using a wire
between the ECM terminal 10 and the TCM
terminal D14. When the engine is warm the ECM
connects its terminal 10 to ground using a Low
Side Driver. When the engine is Cold the ECM
lets this wire open and the TCM pulls it up to 5
volts.
•
When Ignition is ON and Engine is OFF: the ECM
always sends the information “engine cold” even
if the engine is warm. The information is valid
only when the engine is ON.
Diagnostic Aids:
•
This Diagnostic is not an electrical test done by
the TCM but a test between different information
(“logic test”).
•
Detection conditions of engine always cold:
1 Engine seen as cold: wire short to voltage or
open.
2 Transmission Oil Temperature >150°C (302°F)
or more than 20 minutes since last ignition
cycle.
3 Detection conditions need to be present for at
least 25 seconds.
•
Detection conditions of engine always warm:
1 Engine seen as warm: wire short to ground.
2 Transmission Oil Temperature < 0°C (32°F).
3 Without problem on Transmission Tem-
perature sensor then: voltage on A/T Oil
Temperature sensor <4.74 V.
4 Detection conditions need to be present for at
least 6 seconds.
•
Action after the detection time: No action.
•
Recovery conditions: To recover, Engine Coolant
Temperature change information need to be
present for more than 6 seconds.
ENGINE
COOLANT
TEMPERATURE
INPUT
TRANSMISSION
CONTROL
MODULE (TCM)
C-95
ENGINE
COOLANT
TEMPERATURE
OUTPUT
ENGINE
CONTROL
MODULE (ECM)
10
E-61
6
H-25
BRN
BRN
H-25
BLK
BLK
BLK
7
C1(1)
D1(17)
GROUND
D14(30)
D07LW019