SERVICE MANUAL UPDATE SEC. 6E3 DRIVEABILITY AND EMISSIONS
SUBJECT: SERVICE MANUAL UPDATE - SECTION 6E3 DRIVEABILITY AND EMISSIONS
VEHICLES AFFECTED: 1993 "N" MODEL WITH 2.3L ENGINE (VIN D, A, AND 3)
This Bulletin updates Section 6E3 of the 1993 Pontiac "N" Carline Service Manual with the 2.3L (VIN D, A, and 3) engine. The updated pages are as follows:
- A-9 "On-Board Diagnostic (OBD) System Check" - A-42 DTC 19 Intermittent 7X Reference Circuit - A-66 DTC 43 Knock Sensor (KS) Circuit - C5-2 Chart C-5 Knock Sensor (KS) System Check
Please update your 1993 Pontiac "N" Carline Service Manual accordingly.
The On-Board Diagnostic (OBD) system 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 Tech 1 data listed in the table may be used for comparison, after completing the OBD system check and finding the on-board diagnostics functioning properly and no diagnostic 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 diagnosing. If a scan reads other parameters, the values are not recommended by General Motors for use in diagnosing. 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," Section "B".
TECH 1 DATA
Idle/Upper Radiator Hose Hot/Closed Throttle/Park or Neutral/"Closed Loop"/Acc. "OFF"
Scan Position Units Displayed Typical Data Value Refer to ------------- --------------- ------------------ -------- Engine Speed RPM 100 RPM from desired RPM (+ 50 in drive)
Desired idle RPM ECM idle command (varies with calibration, temp.)
Eng. Coolant Temp. celsius/fahrenheit 85 degrees-115 degrees Celsius
Intake Air Temp. Celsius/Fahrenheit 10 degrees-80 degrees Celsius(depends on underhood temp.)
MAP kPa, V 1-3 volts (depends on vacuum & baro pressure)
BARO kPa, V 3-5 volts (depends on altitude & baro pressure)
Throt Position Volts .200-.900 (up to 5.0 C2 at wide open throttle)
Throttle Angle 0-100% 0% (up to 100% at C2 wide open throttle)
02S mV 1-1000 and varying
injector Pulse m Sec. 1-4 and varying C2 Width
Spark Advance # of Degrees Varies C4
Lo Oct. # of Degrees Varies Knock Ret.
S.T. Fuel Trim Counts Varies
L.T. Fuel Trim Counts 58-198 (see Section " C2
Loop Status Open/Closed "Closed Loop" (may go open with C2 extended idle)
Fuel Trim Cell Cell Number 18-21 at idle (depends on air flow, RPM, P/N & A/C)
Knock Retard Degrees of Retard 0 C5
Knock Signal Yes/No No C5
KS Activity 0-255 Counts 16-22 (usable for DTC 43) C5
7x Resync Counter 0-255 Counts 0 (usable for DTC 19)
Ign. Control 0-255 Counts 0-255 (usable for DTC 19) 7x Ref.
Ign Control "ON/OFF" ON" (usable for DTC 19 and 7x Syn. for misfire diagnosis)
idle Air Control Counts (steps) 5-60 C2
Park/Neutral PN and RDL P-N-- (or -R-DL manual only) Position
VSS Mph and km/h 0 C8
TCC/Shift Light "ON/OFF" "OFF" ("ON," with TCC commanded) C8
System Voltage Volts 13.5 - 14.5 C2
2nd Gear Yes/No (N/A No (yes in 2nd or 3rd gear) L40 only) or yes (man. trans. only)
3rd Gear Yes/No (N/A No (yes in 3rd gear) L40 only) or yes (man. trans. only)
A/C Request Yes/No No (yes, with A/C requested, C10 ie: selector "ON")
A/C Clutch "ON/OFF" "OFF" ("ON," with A/C C10 commanded "ON ")
A/C Clutch "ON/OFF" "OFF" ("ON," with C10 A/C commanded "ON")
A/C Ref. Pressure psi/Volts 0-450 psi (varying with high side refrigerant pressure)
Cool Fan Relay "ON/OFF" "OFF"("ON," with A/C" ON or C12 hot eng)
Fuel EVAP Purge % 0-100% C3
QDM A Low/Hi Low
QDM B Low/Hi Low
QDM C Low/Hi Low
QDM D Low/Hi Low
Calibration ID # Production ECM/Calibration ID (not usable)
Time From Start Min/Sec Varies (engine run time since start)
The Electronic Ignition Control Module (ICM) sends a reference signal to the Engine Control Module (ECM) seven times per revolution to indicate crankshaft position and RPM so that the ECM can determine when to pulse the ignition coils and control ignition timing. This signal is called the 7X reference because it occurs seven times per revolution. The ICM applies 5 volts from terminal "G" through CKT 483 to ECM terminal "PD2" and in effect, switches this circuit to ground for a very short period of time. The seventh pulse is the sync pulse and is used for crankshaft position reference. DTC 19 is set if the ECM misses at least 20 resync pulses within 4 minutes and 16 seconds.
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. This determines if the ECM recognizes a problem. If it doesn't set DTC 19 at this point, the problem is intermittent.
2. When a 7X resync occurs, engine stumble also occurs. If a component connection or circuitry is at fault, engine stumble may be induced by wiggling the circuit or connection. This step determines if a component connection or circuit is at fault.
3. Operating faulty non-engine related electronic components may emit Electromagnetic interference (EMI) which may cause a 7X resync. This step determines if the non-engine related component is at fault.
Diagnostic Aids:
An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation. Inspect ECM harness connector terminal "PD2" and ICM 11 pin connector terminal "G" for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.
If vehicle has non-standard electrical equipment, (such as CB radios, 2-way radios, etc.) check to see if their operation may cause a 7X resync. Faulty wiring or faulty non-standard electrical component operation may cause DTC 19.
If complaint was "Cranks But Will Not Run," DTC 19 may be set when engine start is attempted more than 20 times and ignition is not turned "OFF" between attempts.
Circuit Description:
The knock sensor detects engine detonation and the Engine Control Module (ECM) retards the electronic spark timing based on the signal being received. The knock sensor produces an AC signal which is used for knock detection. The amplitude and signal frequency, are dependent upon the knock level.
The ECM performs two tests on this circuit to determine if it is operating correctly. If either of the tests fail, a DTC 43 will be set.
0 If there is an indication of knock for more than 4.54 seconds over a 5 second interval with the engine running.
0 If ECM terminal "BC 13" does not indicate increasing Knock Sensor (KS) activity with engine speed.
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. If the conditions for the test as described above are being met, DTC 43 will be currently set and the MIL (Service Engine Soon) will be illuminated.
2. The Tech 1 scan tool displays knock sensor activity in counts, approximately 16-22 at idle. The counts should rise when engine speed increases or fall when engine speed decreases. This step checks knock sensor activity.
3. This step checks that the internal resistance of knock sensor is within an acceptable range.
4. If the engine has an internal problem which is creating a knock, the knock sensor may be responding to the mechanical noise.
Diagnostic Aids:
Check CKT 496 for a potential open or short to ground.
Also check for proper installation of the PROM.
Refer to "Intermittents" in "Symptoms," Section "6E3-B".
An "Intermittent" problem may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.
Anv circuitry, that is suspected as causing the intermittent complaint, should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness.
Mechanical engine knock can cause a knock sensor signal. Abnormal engine noise must be corrected before using this chart.
Circuit Description:
The knock sensor is used to detect engine detonation and the Engine Control Module (ECM) will retard the electronic spark timing based on the signal being received. The knock sensor produces an AC signal. The amplitude and frequency are dependent upon the knock level.
The PROM used with this engine contains the functions which were part of remotely mounted Knock Sensor (KS) modules used on other GM vehicles. The KS portion of the PROM then sends a signal to other parts of the ECM which adjusts the spark timing to retard the spark and reduce the detonation.
Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. The Tech 1 scan tool displays knock sensor activity in counts, approximately 16-22 at idle. The counts should rise when engine speed increases or fall when engine speed decreases. This step checks knock sensor activity.
2. This step checks that the internal resistance of knock sensor is within an acceptable range.
3. If the engine has an internal problem which is creating a knock, the knock sensor may be responding to the mechanical noise.
Diagnostic Aids:
While observing knock signal on the Tech 1 scan tool, there should be an indication that knock is present when detonation can be heard. Detonation is most likely to occur under high engine load conditions.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
