3UR-FE ENGINE CONTROL: SFI SYSTEM: CAUTION / NOTICE / HINT (2008 Sequoia)

Last Modified: 11-29-2007		1.6 C
Service Category: Engine/Hybrid System	Section: Engine Control
Model Year: 2008	Model: Sequoia	Doc ID: RM000000TB302WX
Title: 3UR-FE ENGINE CONTROL: SFI SYSTEM: CAUTION / NOTICE / HINT (2008 Sequoia)

DTC

P0128

Coolant Thermostat (Coolant Temperature Below Thermostat Regulating Temperature)

CAUTION / NOTICE / HINT

DESCRIPTION

This DTC is stored when the Engine Coolant Temperature (ECT) does not reach 75°C (167°F) despite sufficient engine warm-up time having elapsed.

DTC No.	DTC Detection Condition	Trouble Area
P0128	Conditions (a), (b) and (c) met for 5 seconds (2 trip detection logic): (a) Cold start (b) Engine warmed up (c) ECT less than 75°C (167°F)	Thermostat Cooling system ECT sensor ECM

MONITOR DESCRIPTION

The ECM estimates the ECT based on the starting temperature, engine loads, and engine speeds. The ECM then compares the estimated temperature with the actual ECT. When the estimated ECT reaches 75°C (167°F), the ECM checks the actual ECT. If the actual ECT is less than 75°C (167°F), the ECM interprets this as a malfunction in the thermostat or the engine cooling system and stores the DTC.

MONITOR STRATEGY

Related DTCs	P0128: Coolant Thermostat
Required Sensors/Components (Main)	Thermostat
Required Sensors/Components (Related)	Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, Vehicle speed sensor
Frequency of Operation	Once per driving cycle
Duration	900 seconds
MIL Operation	2 driving cycles
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever following DTCs not present	P0010 , P0020 (VVT OCV) P0011 (VVT System 1 - Advance) P0012 (VVT System 1 - Retard) P0021 (VVT System 2 - Advance) P0022 (VVT System 2 - Retard) P0031, P0032, P0051, P0052 (A/F Sensor Heater - Sensor 1) P0102 - P0103 (MAF meter) P0110 - P0113 (IAT sensor) P0115 - P0118 (ECT sensor) P0125 (Insufficient ECT for Closed Loop) P0171, P0172 (Fuel system) P0300 - P0308 (Misfire) P0335 (CKP sensor) P0340 - P0346 (VVT sensor 1, 2) P0351 - P0358 (Igniter) P0500 (VSS) P2196, P2198 (A/F sensor - rationality) P2237, P2240 (A/F sensor - open) P2A00, P2A03 (A/F sensor - slow response)
Battery voltage	11 V or more
Either of following conditions 1 or 2 met:	-
1. All of following conditions met:	-
ECT at engine start - IAT at engine start	-15 to 7°C (-27 to 12.6°F)
ECT at engine start	-10 to 56°C (14 to 133°F)
IAT at engine start	-10 to 56°C (14 to 133°F)
2. All of following conditions met:	-
ECT at engine start - IAT at engine start	More than 7°C (12.6 °F)
ECT at engine start	56°C (133°F) or less
IAT at engine start	-10°C (14°F) or more
Accumulated time at 128 km/h (80 mph) or more of vehicle speed	Less than 20 seconds

TYPICAL MALFUNCTION THRESHOLDS

Duration that both of following conditions (a) and (b) met	5 seconds or more
(a) Estimated ECT	75°C (167°F) or more
(b) ECT sensor output	Below 75°C (167°F)

INSPECTION PROCEDURE

HINT:

This DTC relates to the thermostat.
Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE

1.	CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0128)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read DTCs.

Result

Result	Proceed to
P0128 is output	A
P0128 and other DTCs are output	B

HINT:

If any DTCs other than P0128 are output, troubleshoot those DTCs first.

2.	CHECK COOLING SYSTEM

(a) Check for defects in the cooling system that might cause the system to be too cold, such as abnormal radiator fan operation or any modifications.

3.	INSPECT THERMOSTAT

(a) Remove the thermostat .

(b) Measure the valve opening temperature of the thermostat.

Standard opening temperature:

80 to 84°C (176 to 183°F)

HINT:

In addition to the above check, confirm that the valve is completely closed when the temperature is below the standard.