Pontiac Fiero 1988 Service Manual page 463

6E2-A-8 DRIVEABILITY AND EMISSIONS - FUEL INJECTION (TBI)
DIAGNOSTIC CIRCUIT CHECK
The Diagnostic Circuit Check is an organized approach to identifying a problem created by an Electronic
Engine Control System malfunction. It must be the starting point for any driveability complaint diagnosis,
because it directs the Service Technician to the next logical step in diagnosing the complaint.
The "Scan Data" listed in the table may be used for comparison, after completing the Diagnostic Circuit
Check and finding the on-board diagnostics functioning properly and no trouble codes displayed. The "Typical
Values" are an average of display values recorded from normally operating vehicles and are intended to
represent what a normally functioning system would typically display.
A "SCAN" TOOL THAT DISPLAYS FAULTY DATA SHOULD NOT BE USED, AND THE PROBLEM
SHOULD BE REPORTED TO THE MANUFACTURER. THE USE OF A FAULTY "SCAN" CAN RESULT
IN MISDIAGNOSIS AND UNNECESSARY PARTS REPLACEMENT.
Only the parameters listed below are used in this manual for diagnosis. If a "Scan" reads other parameters,
the values are not recommended by General Motors for use in diagnosis. For more description on the values and
use of the "Scan" to diagnosis ECM inputs, refer to the applicable diagnosis section in Section C. If all values are
within the range illustrated, refer to symptoms in Section B.
"SCAN" DATA
Idle / U p p e r R a d i a t o r Hose H o t / Closed T h r o t t l e / Park o r N e u t r a l / Closed L o o p / Acc o f f
" S C A N " Position
Units Displayed Typical D a t a V a l u e
Desired RPM RPM ECM idle command (varies w i t h temp.)
RPM RPM ± 50 RPM f r o m desired RPM in drive(Auto)
± 100 RPM f r o m desired RPM in neutral (Manual)
Coolant Temp.
C° 85°-105°
MAT Temp.
C° 10° - 90° (varies w i t h underhood t e m p .
and sensor location)
MAP
Volts
1 - 2 (depends on Vac. & Baro pressure)
BPW (base pulse w i d t h ) M/Sec . 8 - 3 . 0
0
2
Volts . 1 - 1 and varies
TPS Volts
.4-
1.25
Throttle Angle 0 - 1 0 0 % 0
IAC
Counts (steps) 1 - 50
P/N Switch
P/N and RDL Park/Neutral (P/N)
INT (Integrator)
Counts 1 1 0 - 1 4 5
BLM (Block Learn)
Counts 118- 138
Open/Closed Loop Open/Closed Closed Loop (may go open w i t h extended idle)
VSS MPH
0
TCC On/Off Off/ (on w i t h TCC commanded)
Spark Advance # of Degrees Varies
Battery Volts 13.5- 14.5
Fan On/Off Off (below 102°C)
A/C Request Yes/No No (yes, w i t h A/C requested)
A/C Clutch
On/Off Off (on, w i t h A/C commanded on)
Shift Light (M/T)
On/Off Off
11-19-86
* 7S 3604-6E