1988 JEEP CHEROKEE Service Repair Manual

Fig. 14: Typical Pulsed Secondary Air Injection System
Courtesy of General Motors Corp.
OXYGEN SENSOR (O2)
The O2 sensor is mounted in the exhaust system where it
monitors oxygen content of exhaust gases. Some vehicles may use 2 O2
sensors. The O2 sensor produces a voltage signal which is proportional
to exhaust gas oxygen concentration (0-3%) compared to outside oxygen
(20-21%). This voltage signal is low (about .1 volt) when a lean
mixture is present and high (1.0 volt) when a rich mixture is present.\
As ECM compensates for a lean or rich condition, this voltage
signal constantly fluctuates between high and low, crossing a
reference voltage supplied by the ECM on the O2 signal line. This is
referred to as cross counts. A problem in the O2 sensor circuit should
set a related trouble code.
COMPUTERIZED ENGINE CONTROLS (CEC)
The CEC system monitors and controls a variety of
engine/vehicle functions. The CEC system is primarily an emission
control system designed to maintain a 14.7:1 air/fuel ratio under most
operating conditions. When the ideal air/fuel ratio is maintained, the
catalytic converter can control oxides of nitrogen (NOx), hydrocarbon
(HC) and carbon monoxide (CO) emissions.
The CEC system consists of the following sub-systems:
Electronic Control Module (ECM), input devices (sensors and switches)\
and output signals.

EARLY FUEL EVAPORATION (EFE)
The EFE valve is actuated by either a vacuum actuator or a
bimetal spring (heat-riser type). The EFE valve is closed when engine
is cold. The closed valve restricts exhaust gas flow from the exhaust
manifold. This forces part of the exhaust gas to flow up through a
passage below the carburetor. As the exhaust gas quickly warms the
intake mixture, distribution is improved. This results in better cold
engine driveability, shorter choke periods and lower emissions.
Ensure EFE valve in exhaust manifold is not frozen or rusted
in a fixed position. On vacuum-actuated EFE system, check EFE thermal
vacuum valve and check valve(s). Also check for proper vacuum hose
routing. See Fig. 15.
Fig. 15: Typical Vacuum-Actuated EFE System
Courtesy of General Motors Corp.
EMISSION MAINTENANCE REMINDER LIGHT (EMR) (IF EQUIPPED)

If equipped, the EMR light (some models may use a reminder
flag) reminds vehicle operator that an emission system maintenance is
required. This indicator is activated after a predetermined
time/mileage.
When performing a smog check inspection, ensure EMR indicator
is not activated. On models using an EMR light, light should glow when
ignition switch is turned to ON position and should turn off when
engine is running.
If an EMR flag is present or an EMR light stays on with
engine running, fail vehicle and service or replace applicable
emission-related components. To reset an EMR indicator, refer to
appropriate MAINTENANCE REMINDER LIGHTS in the MAINTENANCE section.
MALFUNCTION INDICATOR LIGHT (MIL)
The Malfunction Indicator Light (MIL) is used to alert
vehicle operator that the computerized engine control system has
detected a malfunction (when it stays on all the time with engine
running). On some models, the MIL may also be used to display trouble
codes.
As a bulb and system check, malfunction indicator light will
glow when ignition switch is turned to ON position and engine is not
running. When engine is started, light should go out.

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EM IS SIO NS R EC ALL # 617 - O XYG EN S EN SO R & C AT. C O NV.

1 988 J e ep C hero ke e
EMISSION RECALL BULLETIN
EMISSIONS RECALL #617 - OXYGEN SENSOR AND CATALYTIC CONVERTER
Model(s): 1989 and 1990 Jeep Cherokee (XJ), Comanche (MJ) and\
Wrangler (YJ) Vehicles Equipped With a 2.5L Engine and
a Federal Emission Control System and Built After
November 27, 1988
Bulletin No.: 617
Date: May, 1995
NOTE: This is an Emission Recall bulletin.
VEHICLES AFFECTED
1989 and 1990 Jeep Cherokee (XJ), Comanche (MJ) and Wrangler (YJ)\
Vehicles Equipped With a 2.5L Engine and a Federal Emission Control
System and Built After November 27, 1988.
SERVICE INFORMATION
Failure of the oxygen sensor and catalytic converter on the listed
models, may cause a vehicle to be in violation of U.S Environmental
Protection Agency (EPA) Emissions Standards. To correct this
condition, the oxygen sensor and catalytic converter must be replaced
with improved design parts.
Details of this service action are explained in the following
sections.
SERVICE PROCEDURE VIDEOTAPE
No videotape of the service procedure for this recall will be
provided.
DEALER NOTIFICATION & VEHICLE LIST
INVOLVED DEALERS
Each dealer to whom involved vehicles were invoiced (or the current
dealer at the same street address) will receive a copy of this dealer
recall notification letter and a list of the involved vehicles by
first class mail.
The Vehicle List is arranged in Vehicle Identification Number (VIN)
sequence. Owners known to Chrysler are also listed. The lists are for
dealer reference in arranging for service of involved vehicles as
necessary.
ALL OTHER DEALERS
Each Jeep & Eagle dealer who does not receive a Vehicle List will
receive a copy of this dealer recall notification letter by first
class mail.
DIAL SYSTEM FUNCTION 70

All involved vehicles will be entered to DIAL System Function 70 at
the time of recall implementation for dealer inquiry by VIN as needed.
PARTS
IMPORTANT: A quantity of parts will be distributed initially and
billed to all involved dealers. This quantity will cover
a portion of the total vehicles involved. Additional parts
may be ordered as needed to support customer demand.
Each involved dealer, to whom vehicles in the recall were invoiced
(or the current dealer at the same street address), will receive
enough Emission Service Packages, Recall PN C3906170, to service 25%
of those vehicles.
Each parts package contains the following components:
EMISSION SERVICE PACKAGE







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Qty  Description  Qty  Description 






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1  Oxygen Sensor  1  Clamp 

1  Catalytic Converter  4  Bolts 

1  Gasket  4  Nuts 

1  Recall Completion Label  1  Instruction Sheet 










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OWNER NOTIFICATION & SERVICE SCHEDULING
All involved vehicle owners known to Chrysler are being notified of
the service requirement by first class mail. They are requested to
schedule appointments for the service with their dealers at the
earliest possible date. A copy of the
CUSTOMER NOTIFICATION LETTER is
in this bulletin.
Enclosed with each owner notification is an Owner Notification Form.
The involved vehicle and recall are identified on the form for owner
or dealer reference as needed.
SERVICE PROCEDURE
A. Replace Oxygen Sensor
1. Locate the oxygen sensor in the exhaust manifold as shown in
Fig. 1 .
2. Disconnect the oxygen sensor electrical connector.
3. Remove the oxygen sensor.
4. Clean the exhaust manifold threads using a thread chaser.
NOTE: Do not use solvents or lubricants on threads.
5. Install provided oxygen sensor. Tighten to 22 ft-lbs (30 N-m)
6. Connect oxygen sensor electrical connector.

Fig. 1: Oxygen Sensor Location
B. Replace Catalytic Converter
WARNING: IF TORCHES ARE USED WHEN WORKING ON THE EXHAUST SYSTEM,
DO NOT ALLOW THE FLAME NEAR THE FUEL LINES.
1. Remove and discard the nuts, bolts and gasket at the front of the
converter and the exhaust pipe clamp at the rear (see Fig. 2).
NOTE: Use penetrating oil if necessary.

2. On Wrangler (YJ) vehicles: Support the transmission and remove the
skid plate.
3. Place a block of wood against the rear of the converter and drive
the clamp converter forward to disengage the alignment tab on the
converter pipe from the alignment slot on the muffler.
Fig. 2: Removing Converter and Exhaust Pipe Clamp
NOTE: If the converter does not move forward, it may be necessary to
heat the converter to muffler connection with an oxyacetylene
torch until the metal becomes cherry red.
4. Twist the converter back and forth to separate it from the muffler.
5. Install the new converter into the muffler until the alignment tab
is inserted into the alignment slot.
6. Using the provided gasket, nuts and bolts, attach the converter to
the front exhaust pipe. Do not tighten the bolts.
7. Install and tighten the new exhaust pipe clamp, at the muffler to
converter connection, to 40 ft-lbs (57 N-m).
8. Tighten the converter to front exhaust pipe bolts to 25 ft-lbs
(34 N-m).
9. On Wrangler (YJ) vehicles: Install the skid plate.
10. Lower vehicle.
C. Install Recall Completion Label
1. With a ball point pen, print your dealer code (5 digits) on the
supplied Recall Completion Label.

2. Peel the label from its backing and apply it near the Vehicle
Emissions Control Information Label on the underside of the hood.
D. Complete Proof of Correction Form
1. Complete a Vehicle Emission Recall Proof of Correction Form and
supply it to the vehicle owner.
COMPLETION REPORTING AND REIMBURSEMENT
Claims for vehicles which have been serviced must be submitted on
the DIAL System Claims submitted will be used by Chrysler to record
recall service completions and provide dealer payments.
Use the following labor operation number and time allowance:
Labor
Operation Time
Number Allowance




















Replace oxygen sensor and catalytic converter 25617182 0.8 Hours
Add the cost of the recall parts package plus applicable dealer
allowance to your claim.
PARTS RETURN
Removed catalytic converters must be returned to the Warranty
Material Return Center.
NOTE: See Warranty Policy and Procedure Manual, Chapter 6, Subsection
H for complete recall claim processing and material return
instructions.
VEHICLE NOT AVAILABLE
If a vehicle is not available for service for a known reason, let us
know by filling out the pre-addressed Vehicle Disposition Form portion
of the Owner Notification Form, or describe the reason on a postcard
and mail to:
Chrysler Corporation 429-10-04
P.O. Box 1919
Detroit, Michigan 48231-1919
Following the above procedures will expedite the processing of your
claim.
If you have any questions or need assistance in completing this
action, please contact your Zone Service Office.
Customer Services Field Operations
Chrysler Corporation
CUSTOMER NOTIFICATION LETTER









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EMISSIONS RECALL TO REPLACE YOUR VEHICLE'S
OXYGEN SENSOR AND CATALYTIC CONVERTER
Dear Jeep Vehicle Owner: