| Subject: | Check Engine Light On with No Drivability Concerns, DTC P0120,
P0220, P1516, or P1518 Set (Clear Code) |
| Models: | 2003 Cadillac Escalade, Escalade EXT, Escalade ESV |
| 2003
Chevrolet Avalanche, Silverado, Suburban, Tahoe |
| 2003 GMC Sierra, Yukon, Yukon XL |
| with 4.8L, 5.3L or 6.0L Engine (VINs V, P, T, Z, N, U - RPOs LR4, LM4, LM7,
L59, LQ9, LQ4,) |
Condition
Some owners may comment that the Check Engine Light is illuminated and there
is no driveability concern. Upon investigation, the technician may find codes P0120,
P0220, P1516 or P1518. Also, technicians may note that low voltage codes P0562, P0563,
P1637 or P1638 have been set.
Cause
The Tach module may set the code in error if it operates at a battery voltage
of 4.5 to 5.0 volts.
Correction
If the vehicle has stored one of the low voltage codes, P0562, P0563, P1637
or P1638, follow the appropriate diagnostics for the low voltage code. In most cases,
this will lead to correcting the concern without replacing any Electronic Throttle
Control (ETC) components.
If codes P0120, P0220, P1516 or P1518 are present without any of the low voltage
codes, the technician should observe the Engine RPM in the fault record.
| • | If the Engine RPM in the fault record is zero and the customer indicates
that the vehicles has experienced a low voltage condition, the code should be cleared
and the low voltage should be diagnosed and corrected. |
| • | If the Engine RPM is zero and the customer indicates that there have been
no low voltage conditions, then the P1516 diagnostic aids for intermittent concerns
should be used to diagnose and correct the vehicle |
| • | If the Engine RPM is greater than zero, then check for an obvious loose
ground at G103 located next to the right cylinder head just below the head and mounted
into the block. Also, check G104 located behind the left cylinder head. Then verify
all electrical connections at the TAC module. |
If the concern is still not resolved, contact Technical Assistance.
Warranty Information
For vehicles repaired under warranty, use the applicable labor operation for
the repair performed.
