2000-2001 ISUZU V-6 Electronic Throttle Control (IB00-04-S006)

2000-2001 ISUZU V-6 ELECTRONIC THROTTLE CONTROL

TECHNICAL SERVICE BULLETIN

Affected Vehicles

All 2000 - 2001 Isuzu V-6 engines with Electronic Throttle Control.

Service Information

All 2000 - 2001 Isuzu V-6 engines with Electronic Throttle Control may exhibit multiple codes for any condition identified in the Accelerator Pedal Assembly and/or the Throttle Assembly. In order to clarify the diagnostics available with the Tech 2 and the PowerLink, this bulletin will present four possible symptoms that actually help identify the root cause.

The Isuzu Electronic Throttle Control System will usually set multiple codes no matter which driveability symptoms are present. To best diagnose the condition, the service advisor and technician should ask the customer when the MIL and Reduced Power Light sets and if any driveability symptoms were present. The most common  codes associated with their respective sensor and/or throttle motor circuits are:

CODE(S)	RESULTS
P1271, P1273, and P1275.	AP1 SIGNAL CONDITION.
P1271, P1272, and P1280.	AP2 SIGNAL CONDITION.
P0452, P1120, P1125, P1221, P1271, P1272, P1273, P1275, P1285, and P1635.	AP1 REFERENCE CONDITION.
P1220, P1221, P1271, P1272, P1280, and P1639.	AP2 REFERENCE CONDITION.
P1272, P1273, and P1285.	AP3 SIGNAL CONDITION.
P1125, P1221, P1271, P1273, P1275, P1285, P1295, P1299, and P1515.	AP3 REFERENCE CONDITION.
P1120 and P1221	TP1 SIGNAL CONDITION.
P0405, P0452, P1120, P1125, P1221, P1271, P1272, P1273, P1275, and P1635.	TP1 REFERENCE CONDITION.
P1220 and P1221	TP2 SIGNAL CONDITION.
P1220, P1221, P1271, P1272, P1280, and P1639.	TP2 REFERENCE CONDITION.
P1125, P1295, P1515, and P1516.	THROTTLE MOTOR CONDITION.

The four most common symptoms associated with Electronic Throttle are:

• The Reduced Power Light may be on with the MIL on/off with no driveability symptoms existing at the time of code detection or during diagnostics. Usually P1271, P1273 and P1275 are stored in memory. The code(s) set at key-up and are related to correlation errors. Remember, when the TP1 and the TP2 or the AP1 and the AP2 actual readings are added together, the total should be 100%. If the variation is at or exceeds 5%, a P1275 may set. In order to duplicate the condition, install the Tech 2 or the PowerLink and perform a quick-snapshot prior to the initial cold start. Look for a glitch on the AP1 reading.
• The second complaint will usually be related to the MIL and Reduced Power Light with codes for throttle position sensors or accelerator position sensors. The customer will also complain of lack-of-power. This condition is most likely related to loss of a five-volt reference. Therefore one AP sensor and one TP sensor are affected. A P1275 is definitely present.
• The third complaint will also be related to the Reduced Power Light being on, the MIL on and the vehicle in a "Forced Idle" mode. This may be related to loss of both five-volt references, loss of both AP sensor readings, and/or loss of both TP sensor readings.
• The final complaint is also related to a Reduced Power Light present, the MIL on, and a forced shut-down condition. The vehicle will crank but will not start. This condition may be related to a Throttle Motor condition and/or the loss of either or both five-volt references for the Throttle Position Sensors and the Accelerator Position Sensors.

Use this bulletin as a guide in determining the direction and starting point of diagnostics for the Isuzu V-6 Electronic Throttle Systems.