1999 TOYOTA 4RUNNER 3.4L V6 Emission : Oxygen Sensor Auto Parts - RockAuto.Com 1999 TOYOTA 4RUNNER 3.4L V6 Emission : Oxygen Sensor Auto Parts®
Log In or Create Account (Optional)

AUTO PARTS PRICE COMPARISON
2009 Chevrolet Suburban
Belt Tensioner

Parts Store Part Brand Price
RockAuto Gates $38.79
AutoZone Duralast $54.99
NAPA NAPA $59.99
Advance Gates $62.21
O’Reilly Gates $63.99
(Regular Prices as of 11/26/2014)
Shopping
FAQ  FAQ
Policies
Gift Certificates
Order Status & Returns
Language
Espa˝ol
Deutsch
Franšais
Company Info
Newsletter   RSS Feed
About Us
Careers
Resources
Manufacturers
Warranties
Owner Clubs & Links
Repair Index


Welcome! This is our traditional HTML catalog. Please click here for our Interactive Catalog with more cool features!Add parts to the cart and then enter your country and postal code to see shipping costs.Everything is in stock unless marked "Non-stock."
(0)
Filter By Keyword(s):
Related Parts
Choose for Me to Minimize Cost  
All Vehicles > TOYOTA > 1999 > 4RUNNER > 3.4L V6 > Emission > Oxygen Sensor
1999 TOYOTA 4RUNNER 3.4L V6 : Emission : Oxygen Sensor  PriceAdd to Cart
BECK/ARNLEY Part # 1564063 More Info
Downstream; W/Calif. Emis.; 4WD [Wholesaler Closeout -- 30 Day Warranty] (Only 2 Remaining)
 
$26.84
ULTRAPOWER Part # 2344161 More Info   One of our most popular parts
4 WHEEL/ALL WHEEL DRIVE Except AUTO TRANS and Except CALIF equipped,UPSTREAM
 
$31.79
ULTRAPOWER Part # 2344154 More Info
4 WHEEL/ALL WHEEL DRIVE Except AUTO TRANS and Except CALIF equipped,DOWNSTREAM
 
$35.79
ULTRAPOWER Part # 2344155 More Info
CALIF equipped Except 4 WHEEL/ALL WHEEL DRIVE,DOWNSTREAM
 
$35.79
NTK Part # 24553 More Info NTK OE Type
Downstream; 4WD; Calif. Emissions; OE Equivalent
Downstream; RWD; Federal Emissions; OE Equivalent
Choose:
See Options at Left
NTK Part # 24554 More Info NTK OE Type
Upstream; Federal Emissions; OE Equivalent
Downstream; 4WD; Federal Emissions; OE Equivalent
Choose:
See Options at Left
ULTRAPOWER Part # 2344162 More Info   One of our most popular parts
Except AUTO TRANS and Except CALIF equipped and Except 4 WHEEL/ALL WHEEL DRIVE,DOWNSTREAM; UPSTREAM
w/AUTO TRANS Except CALIF equipped,DOWNSTREAM; UPSTREAM
 
$37.79
APWI Part # AP444 More Info
Calif. ESV; Downstream; RWD
 
$38.79
NTK Part # 24555 More Info {#24140} NTK OE Type
Downstream; RWD; Calif. Emissions; OE Equivalent
Choose:
See Options at Left
BOSCH Part # 13104 More Info {#13575} OE Style Oxygen Sensor; Heated; Wires: 4; Length (in): 11  One of our most popular parts
Upstream; Automatic trans.; OE manufactured part; without California Emissions
Downstream; 4WD; OE manufactured part; without California Emissions
$42.79
BOSCH Part # 13095 More Info OE Style Oxygen Sensor; Heated; Wires: 4; Length (in): 17.9  One of our most popular parts
Upstream; RWD; Standard trans.; OE manufactured part; To 09/1998; without California Emissions
Downstream; 4WD; OE sensor technology; Replacement item; with California Emissions
Downstream; RWD; OE manufactured part; without California Emissions
Downstream; 4WD; Automatic trans.; SR5 Model; OE manufactured part; with California Emissions
$42.79
STANDARD MOTOR PRODUCTS Part # SG376 More Info
Downstream Sensor; 4WD; Fed.
Downstream Sensor; 2WD; Fed.
[Wholesaler Closeout - Private Label Pkg. - 30 Day Warranty]
$43.79
DENSO Part # 2344162 More Info {#8946509020, 8946509140, 8946509190, 8946509210, 8946509220, 8946509310, 8946509320, 894650C200, 8946539735, 8946539835, 8946539865, 8946580034} OE Style; Includes Gasket  One of our most popular parts
Upstream; DENSO is the O.E. Manufacturer / Exc. Calif.
Downstream; DENSO is the O.E. Manufacturer / Exc. Calif.
 
$44.79
DENSO Part # 2344154 More Info {#8946509040, 8946509110, 8946509170, 8946509180, 8946539605, 8946539655, 8946539665, 8946539855, 8946539885, 8946569175, 8946580011} OE Style  One of our most popular parts
Downstream; 4WD; Standard trans.; DENSO is the O.E. Manufacturer / Exc. Calif.
 
$44.79
DENSO Part # 2344153 More Info {#8946509030, 8946509050, 8946509070, 8946509080, 8946509230, 8946529795, 8946539785, 8946539825, 8946539875, 8946549105, 8946549135, 8946569105} OE Style; Wire Length : 17.72"  One of our most popular parts
Downstream; 4WD; DENSO is the O.E. Manufacturer / Calif.
 
$47.79
DENSO Part # 2344161 More Info {#8946509100, 8946509130, 8946509150, 8946509160, 8946509240, 8946509300, 8946509380, 8946509390, 894650C220, 8946529825, 8946539755, 8946539895, 8946580035} OE Style; Includes Gasket  One of our most popular parts
Upstream; 4WD; Standard trans.; DENSO is the O.E. Manufacturer / Exc. Calif.
 
$48.79
WALKER PRODUCTS Part # 25024154 More Info
Upstream; Non-California Emissions Standard Vehicle
Downstream; 4WD; Non-California Emissions Standard Vehicle
 
$48.79
WALKER PRODUCTS Part # 25024153 More Info
Downstream; RWD; Non-California Emissions Standard Vehicle
 
$49.79
DENSO Part # 2344155 More Info {#8946529675, 8946539635, 8946539705, 8946580029} OE Style
Downstream; RWD; DENSO is the O.E. Manufacturer / Calif.
 
$50.79
WALKER PRODUCTS Part # 25024155 More Info
Downstream; California Emissions Standard Vehicle
 
$51.79
BOSCH Part # 15418 More Info OE Style Oxygen Sensor; Heated; Wires: 4; Length (in): 14.6
Upstream; 4WD; Standard trans.; OE sensor technology; without California Emissions
Upstream; RWD; Standard trans.; From 10/1998; OE sensor technology; without California Emissions
$53.79
BOSCH Part # 13142 More Info OE Style Oxygen Sensor; Heated; Wires: 4; Length (in): 23.5
Downstream; RWD; OE manufactured part; with California Emissions
$55.79
BOSCH Part # 13141 More Info OE Style Oxygen Sensor; Heated; Wires: 4; Length (in): 16.5
Downstream; 4WD; OE sensor technology; with California Emissions
* Stocked in outlying warehouse--shipping delayed up to 2 business days
$60.79
DELPHI Part # ES20071 More Info
Downstream; 4WD; SR5 Model; Wrench Size: 7/8 in.
$61.79
DELPHI Part # ES20072 More Info
SR5 Model; Wrench Size: 7/8 in.; Except California
$63.79
AIRTEX / WELLS Part # 5S4081 More Info {#8946535490, 8946580029, SU4964}
RWD; with California Emissions, Located After Converter
* Stocked in outlying warehouse--shipping delayed up to 1 business day
$66.89
DELPHI Part # ES20192 More Info
Downstream; RWD; SR5 Model; Wrench Size: 7/8 in. (Only 2 Remaining)
$67.89
STANDARD MOTOR PRODUCTS Part # SG821 More Info {#8946539635, 8946539705, 8946580029}
Downstream; RWD; w/ Calif. Emissions [Wholesaler Closeout -- 30 Day Warranty] (Only 1 Remaining)
$68.79
STANDARD MOTOR PRODUCTS Part # SG1839 More Info {#8946509020, 8946509040, 8946509070, 8946509110, 8946509140, 8946509170, 8946509180, 8946509190, 8946509220, 8946509310, 8946509320, 8946539605, 8946539655, 8946539735, 8946539835, 8946539855, 8946539865, 8946539885, 8946569175, 8946580011, 8946580034, SG375, SG597, SG786}
Downstream; w/ Federal Emissions
Upstream; w/ Federal Emissions
$72.79
AIRTEX / WELLS Part # 5S4037 More Info {#8946539825, SU4932}
RWD; Exc. with California Emissions, Located After Converter
* Stocked in outlying warehouse--shipping delayed up to 1 business day
$75.79
STANDARD MOTOR PRODUCTS Part # SG1838 More Info {#8946509030, 8946509050, 8946509150, 8946509160, 8946509240, 8946509300, 8946509380, 8946509390, 8946529795, 8946529825, 8946539665, 8946539755, 8946539785, 8946539825, 8946539875, 8946539895, 8946549105, 8946549135, 8946569105, 8946580035, SG561, SG584, SG781, SG783, SG805, SG806, SG835, SG841}
Upstream; 4WD; Standard trans.; w/ Federal Emissions
Downstream; 4WD; w/ Calif. Emissions
$76.89
AIRTEX / WELLS Part # 5S4053 More Info {#8946535270, 8946539605, 8946539735, 8946539835, 8946539855, 8946539865, 8946539885, 8946580034, 8946580036, SU4934}
Automatic trans.; Located Before Converter
4WD; Exc. with California Emissions, Located After Converter
* Stocked in outlying warehouse--shipping delayed up to 1 business day
$77.79
AIRTEX / WELLS Part # 5S4086 More Info {#8946535400, 8946539895, 8946580035, SU4938}
Standard trans.; Located Before Converter
* Stocked in outlying warehouse--shipping delayed up to 1 business day
$83.79
BECK/ARNLEY Part # 1564064 More Info
Downstream; W/Calif. Emis.; RWD (Only 3 Remaining)
 
$85.79
MAGNETI MARELLI Part # 1AMOX00018 More Info
Downstream; RWD; without California Emissions
Upstream; RWD; without California Emissions
(Only 1 Remaining)
 
$95.79
APWI Part # AP4387 More Info Does Not Include Flange
Calif. ESV; Upstream; RWD
$95.99
ACDELCO Part # 2131435 More Info {#19138018, 2133883, 88929862} Professional
Upstream; Non Calif-ESV
Downstream; 4WD; Non Calif-ESV
 
$97.79
ACDELCO Part # 2131434 More Info {#88929861} Professional
Downstream; RWD; Non Calif-ESV
* Stocked in outlying warehouse--shipping delayed up to 1 business day
 
$98.79
ACDELCO Part # 2131436 More Info {#88929863} Professional
Downstream; Calif-ESV
 
$101.89
DENSO Part # 2349002 More Info {#8946735010} OE Style  One of our most popular parts
Upstream; DENSO is the O.E. Manufacturer / Air Fuel Ratio Sensor; Calif.
 
$108.79
DENSO Part # 2349003 More Info {#8946735021} OE Style  One of our most popular parts
Upstream; 4WD; Standard trans.; DENSO is the O.E. Manufacturer / Air Fuel Ratio Sensor; Calif.
 
$110.79
BOSCH Part # 13613 More Info OE Style Oxygen Sensor; Wideband A/F; Wires: 4; Length (in): 12.2  One of our most popular parts
Upstream; Automatic trans.; OE sensor technology; with California Emissions
$116.79
NTK Part # 24669 More Info OE Type 4-Wire A/F Sensor
Upstream; Automatic trans.; Calif. Emissions; OE Equivalent
$120.79
NTK Part # 24670 More Info OE Type 4-Wire A/F Sensor
Upstream; Standard trans.; Calif. Emissions; OE Equivalent
Choose:
See Options at Left
AIRTEX / WELLS Part # 5S4084 More Info {#8946580030, SU4965}
4WD; with California Emissions, Located After Converter
* Stocked in outlying warehouse--shipping delayed up to 1 business day
$127.79
BOSCH Part # 13998 More Info OE Style Oxygen Sensor; Wideband A/F; Wires: 4; Length (in): 16.1
Upstream; Standard trans.; OE sensor technology; with California Emissions
$130.79
DELPHI Part # ES10944 More Info
Upstream; Automatic trans.; SR5 Model; Wrench Size: 7/8 in.; California
$132.79
WALKER PRODUCTS Part # 25054051 More Info
Upstream; Automatic trans; California Emissions Standard Vehicle
 
$139.79
DELPHI Part # ES10945 More Info
Upstream; Standard trans.; SR5 Model; Wrench Size: 7/8 in.; California
$141.79
WALKER PRODUCTS Part # 25054052 More Info
Upstream; Standard trans; California Emissions Standard Vehicle
* Stocked in outlying warehouse--shipping delayed up to 1 business day
 
$145.79
ACDELCO Part # 2132858 More Info {#19107202} Professional
Upstream; Standard trans.; Calif-ESV
* Stocked in outlying warehouse--shipping delayed up to 5 business days
 
$149.89
ACDELCO Part # 2132857 More Info {#19107201} Professional
Upstream; Automatic trans.; Calif-ESV
* Stocked in outlying warehouse--shipping delayed up to 1 business day
 
$224.79
   


Manufacturer & Part #DescriptionNote
STANDARD MOTOR PRODUCTS Part # SG376 Downstream Sensor; 4WD; Fed.
STANDARD MOTOR PRODUCTS Part # SG376 Downstream Sensor; 2WD; Fed.
BOSCH Part # 13095OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 17.9Upstream; RWD; Standard trans.; OE manufactured part; To 09/1998; without California Emissions
BOSCH Part # 13095OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 17.9Downstream; 4WD; OE sensor technology; Replacement item; with California Emissions
BOSCH Part # 13095OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 17.9Downstream; RWD; OE manufactured part; without California Emissions
BOSCH Part # 13095OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 17.9Downstream; 4WD; Automatic trans.; SR5 Model; OE manufactured part; with California Emissions
BOSCH Part # 13104OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 11 (#13575)Upstream; Automatic trans.; OE manufactured part; without California Emissions
BOSCH Part # 13104OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 11 (#13575)Downstream; 4WD; OE manufactured part; without California Emissions
BOSCH Part # 13141OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 16.5Downstream; 4WD; OE sensor technology; with California Emissions
BOSCH Part # 13142OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 23.5Downstream; RWD; OE manufactured part; with California Emissions
ACDELCO Part # 2131434Professional (#88929861)Downstream; RWD; Non Calif-ESV
ACDELCO Part # 2131435Professional (#19138018, 2133883, 88929862)Upstream; Non Calif-ESV
ACDELCO Part # 2131435Professional (#19138018, 2133883, 88929862)Downstream; 4WD; Non Calif-ESV
ACDELCO Part # 2131436Professional (#88929863)Downstream; Calif-ESV
BECK/ARNLEY Part # 1564063 Downstream; W/Calif. Emis.; 4WD
BECK/ARNLEY Part # 1564064 Downstream; W/Calif. Emis.; RWD
BOSCH Part # 13998OE Style Oxygen Sensor Wideband A/F; Wires: 4; Length (in): 16.1Upstream; Standard trans.; OE sensor technology; with California Emissions
BOSCH Part # 13613OE Style Oxygen Sensor Wideband A/F; Wires: 4; Length (in): 12.2Upstream; Automatic trans.; OE sensor technology; with California Emissions
BOSCH Part # 15418OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 14.6Upstream; 4WD; Standard trans.; OE sensor technology; without California Emissions
BOSCH Part # 15418OE Style Oxygen Sensor Heated; Wires: 4; Length (in): 14.6Upstream; RWD; Standard trans.; From 10/1998; OE sensor technology; without California Emissions
ACDELCO Part # 2132858Professional (#19107202)Upstream; Standard trans.; Calif-ESV
ACDELCO Part # 2132857Professional (#19107201)Upstream; Automatic trans.; Calif-ESV
STANDARD MOTOR PRODUCTS Part # SG821(#8946539635, 8946539705, 8946580029)Downstream; RWD; w/ Calif. Emissions
DENSO Part # 2349003OE Style (#8946735021)Upstream; 4WD; Standard trans.; DENSO is the O.E. Manufacturer / Air Fuel Ratio Sensor; Calif.
DENSO Part # 2349002OE Style (#8946735010)Upstream; DENSO is the O.E. Manufacturer / Air Fuel Ratio Sensor; Calif.
DENSO Part # 2344153OE Style Wire Length : 17.72" (#8946509030, 8946509050, 8946509070, 8946509080, 8946509230, 8946529795, 8946539785, 8946539825, 8946539875, 8946549105, 8946549135, 8946569105)Downstream; 4WD; DENSO is the O.E. Manufacturer / Calif.
DENSO Part # 2344155OE Style (#8946529675, 8946539635, 8946539705, 8946580029)Downstream; RWD; DENSO is the O.E. Manufacturer / Calif.
DENSO Part # 2344162OE Style Includes Gasket (#8946509020, 8946509140, 8946509190, 8946509210, 8946509220, 8946509310, 8946509320, 894650C200, 8946539735, 8946539835, 8946539865, 8946580034)Upstream; DENSO is the O.E. Manufacturer / Exc. Calif.
DENSO Part # 2344162OE Style Includes Gasket (#8946509020, 8946509140, 8946509190, 8946509210, 8946509220, 8946509310, 8946509320, 894650C200, 8946539735, 8946539835, 8946539865, 8946580034)Downstream; DENSO is the O.E. Manufacturer / Exc. Calif.
DENSO Part # 2344154OE Style (#8946509040, 8946509110, 8946509170, 8946509180, 8946539605, 8946539655, 8946539665, 8946539855, 8946539885, 8946569175, 8946580011)Downstream; 4WD; Standard trans.; DENSO is the O.E. Manufacturer / Exc. Calif.
DENSO Part # 2344161OE Style Includes Gasket (#8946509100, 8946509130, 8946509150, 8946509160, 8946509240, 8946509300, 8946509380, 8946509390, 894650C220, 8946529825, 8946539755, 8946539895, 8946580035)Upstream; 4WD; Standard trans.; DENSO is the O.E. Manufacturer / Exc. Calif.
AIRTEX / WELLS Part # 5S4081(#8946535490, 8946580029, SU4964)RWD; with California Emissions, Located After Converter
AIRTEX / WELLS Part # 5S4086(#8946535400, 8946539895, 8946580035, SU4938)Standard trans.; Located Before Converter
AIRTEX / WELLS Part # 5S4053(#8946535270, 8946539605, 8946539735, 8946539835, 8946539855, 8946539865, 8946539885, 8946580034, 8946580036, SU4934)Automatic trans.; Located Before Converter
AIRTEX / WELLS Part # 5S4053(#8946535270, 8946539605, 8946539735, 8946539835, 8946539855, 8946539865, 8946539885, 8946580034, 8946580036, SU4934)4WD; Exc. with California Emissions, Located After Converter
AIRTEX / WELLS Part # 5S4084(#8946580030, SU4965)4WD; with California Emissions, Located After Converter
AIRTEX / WELLS Part # 5S4037(#8946539825, SU4932)RWD; Exc. with California Emissions, Located After Converter
DELPHI Part # ES10944 Upstream; Automatic trans.; SR5 Model; Wrench Size: 7/8 in.; California
DELPHI Part # ES20192 Downstream; RWD; SR5 Model; Wrench Size: 7/8 in.
DELPHI Part # ES20072 SR5 Model; Wrench Size: 7/8 in.; Except California
DELPHI Part # ES20071 Downstream; 4WD; SR5 Model; Wrench Size: 7/8 in.
DELPHI Part # ES10945 Upstream; Standard trans.; SR5 Model; Wrench Size: 7/8 in.; California
STANDARD MOTOR PRODUCTS Part # SG1839(#8946509020, 8946509040, 8946509070, 8946509110, 8946509140, 8946509170, 8946509180, 8946509190, 8946509220, 8946509310, 8946509320, 8946539605, 8946539655, 8946539735, 8946539835, 8946539855, 8946539865, 8946539885, 8946569175, 8946580011, 8946580034, SG375, SG597, SG786)Downstream; w/ Federal Emissions
STANDARD MOTOR PRODUCTS Part # SG1839(#8946509020, 8946509040, 8946509070, 8946509110, 8946509140, 8946509170, 8946509180, 8946509190, 8946509220, 8946509310, 8946509320, 8946539605, 8946539655, 8946539735, 8946539835, 8946539855, 8946539865, 8946539885, 8946569175, 8946580011, 8946580034, SG375, SG597, SG786)Upstream; w/ Federal Emissions
STANDARD MOTOR PRODUCTS Part # SG1838(#8946509030, 8946509050, 8946509150, 8946509160, 8946509240, 8946509300, 8946509380, 8946509390, 8946529795, 8946529825, 8946539665, 8946539755, 8946539785, 8946539825, 8946539875, 8946539895, 8946549105, 8946549135, 8946569105, 8946580035, SG561, SG584, SG781, SG783, SG805, SG806, SG835, SG841)Upstream; 4WD; Standard trans.; w/ Federal Emissions
STANDARD MOTOR PRODUCTS Part # SG1838(#8946509030, 8946509050, 8946509150, 8946509160, 8946509240, 8946509300, 8946509380, 8946509390, 8946529795, 8946529825, 8946539665, 8946539755, 8946539785, 8946539825, 8946539875, 8946539895, 8946549105, 8946549135, 8946569105, 8946580035, SG561, SG584, SG781, SG783, SG805, SG806, SG835, SG841)Downstream; 4WD; w/ Calif. Emissions
NTK Part # 24553NTK OE TypeDownstream; 4WD; Calif. Emissions; OE Equivalent
NTK Part # 24553NTK OE TypeDownstream; RWD; Federal Emissions; OE Equivalent
NTK Part # 24554NTK OE TypeUpstream; Federal Emissions; OE Equivalent
NTK Part # 24554NTK OE TypeDownstream; 4WD; Federal Emissions; OE Equivalent
NTK Part # 24669OE Type 4-Wire A/F SensorUpstream; Automatic trans.; Calif. Emissions; OE Equivalent
NTK Part # 24555NTK OE Type (#24140)Downstream; RWD; Calif. Emissions; OE Equivalent
NTK Part # 24670OE Type 4-Wire A/F SensorUpstream; Standard trans.; Calif. Emissions; OE Equivalent
APWI Part # AP4387Does Not Include FlangeCalif. ESV; Upstream; RWD
APWI Part # AP444 Calif. ESV; Downstream; RWD
ULTRAPOWER Part # 2344162 Except AUTO TRANS and Except CALIF EQPD and Except 4 WHEEL/ALL WHEEL DRIVE,DOWNSTREAM; UPSTREAM
ULTRAPOWER Part # 2344162 w/AUTO TRANS Except CALIF EQPD,DOWNSTREAM; UPSTREAM
WALKER PRODUCTS Part # 25024153 Downstream; RWD; Non-California Emissions Standard Vehicle
ULTRAPOWER Part # 2344155 CALIF EQPD Except 4 WHEEL/ALL WHEEL DRIVE,DOWNSTREAM
ULTRAPOWER Part # 2344161 4 WHEEL/ALL WHEEL DRIVE Except AUTO TRANS and Except CALIF EQPD,UPSTREAM
ULTRAPOWER Part # 2344154 4 WHEEL/ALL WHEEL DRIVE Except AUTO TRANS and Except CALIF EQPD,DOWNSTREAM
WALKER PRODUCTS Part # 25024154 Upstream; Non-California Emissions Standard Vehicle
WALKER PRODUCTS Part # 25024154 Downstream; 4WD; Non-California Emissions Standard Vehicle
WALKER PRODUCTS Part # 25024155 Downstream; California Emissions Standard Vehicle
WALKER PRODUCTS Part # 25054051 Upstream; Automatic trans; California Emissions Standard Vehicle
WALKER PRODUCTS Part # 25054052 Upstream; Standard trans; California Emissions Standard Vehicle
MAGNETI MARELLI Part # 1AMOX00018 Downstream; RWD; without California Emissions
MAGNETI MARELLI Part # 1AMOX00018 Upstream; RWD; without California Emissions