DTC 45 Knock Sensor?
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
DTC 45 Knock Sensor?
I pulled the car out of the garage yesterday to crank it and let it warm up. The car idled smoothly for 3-4 minutes and then "bogged down" and started throwing a DTC 45. I cleared the code several times and it returned every time. The car has a LT4 knock module that has been in the car for a year or more. Mods as follows
1. LT4 Hotcam
2. Roller rockers. Cranes 1.6
3. Hooker Headers
4. Recently had a new water pump on and a seal replaced.
5. Opti was in good shape and has about 5k miles on it.
One thing I am thinking about is that I wass running low on fuel one afternoon and ended up buying some mid-grade gas (89 octane) because the station was out of the 91+ Octane stuff.
I did a search and came up with little that directly deals with DTC 45. Looking forward to some input!
1. LT4 Hotcam
2. Roller rockers. Cranes 1.6
3. Hooker Headers
4. Recently had a new water pump on and a seal replaced.
5. Opti was in good shape and has about 5k miles on it.
One thing I am thinking about is that I wass running low on fuel one afternoon and ended up buying some mid-grade gas (89 octane) because the station was out of the 91+ Octane stuff.
I did a search and came up with little that directly deals with DTC 45. Looking forward to some input!
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Are you sure it's DTC 45 and not DTC 43?
DTC 45 would be left front heated O2 sensor.
DTC 43 would be knock sensor circuit.
It seems your car ran ok in open loop (where knock sensors are monitored but O2 sensors are not) and terrible in closed loop.
DTC 45 would be left front heated O2 sensor.
DTC 43 would be knock sensor circuit.
It seems your car ran ok in open loop (where knock sensors are monitored but O2 sensors are not) and terrible in closed loop.
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
Knock sensors can be destroyed by over torquing. Use 14 foot pounds if you wind up replacing the sensors. You probably know this already but they go through the water jackets so a coolant drain is in order when replacing them.
Here's how it works...The sensors should have a constant supply of 5 volts. They contain little crystals that generate an AC signal that rides on the same circuit and when there are no knocks they birng the circuit down to about 1.5 volts. The module listens for that AC signal and when it hears a strong one, it sends a knock event to the PCM which records a knock. Too many knocks in one time frame and the PCM retards ignition timing.
Ok so with the key on "run", engine off, check both terminals in the wire to the knock sensors one for each sensor both sensors for +5 volts to ground.
IF:
Both at 5 volts, check resistance between knock sensor's terminal and ground you should have 3,300-4,500 Ohms. If not replace the sensor that didn't have the correct resistance. If both have the proper resistance, ignition off, disconnect connector D from the PCM, ignitino back on, check for any voltage on ckt 496 (diagram will help find it!) If there is any voltage there, ckt 496 is shorted to another voltage supply. If no voltage is there, one or both of the knock sensors are inop or improperly installed or the module is inop or the PCM is inop.
IF: only one of the sensor's leads has 5 volts, then there is an open wire on its splice. (Both knock sensors are on the same circuit from the module and they are spliced off like a Y)
IF: neither sensor's lead has 5 volts, then there is an open or ground issue between the splice and the PCM or the module or PCM is inop.
Also, check the routing of the wires to the knock sensors. If they come too close to a spark plug wire, the spark can induce a current in the KS circuit and also throw code 43.
Circuit 496 is the line from the KS module to the sensors and is a dark blue wire.
Post up what you find!
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
No worries.
Knock sensors can be destroyed by over torquing. Use 14 foot pounds if you wind up replacing the sensors. You probably know this already but they go through the water jackets so a coolant drain is in order when replacing them.
Here's how it works...The sensors should have a constant supply of 5 volts. They contain little crystals that generate an AC signal that rides on the same circuit and when there are no knocks they birng the circuit down to about 1.5 volts. The module listens for that AC signal and when it hears a strong one, it sends a knock event to the PCM which records a knock. Too many knocks in one time frame and the PCM retards ignition timing.
Ok so with the key on "run", engine off, check both terminals in the wire to the knock sensors one for each sensor both sensors for +5 volts to ground.
IF:
Both at 5 volts, check resistance between knock sensor's terminal and ground you should have 3,300-4,500 Ohms. If not replace the sensor that didn't have the correct resistance. If both have the proper resistance, ignition off, disconnect connector D from the PCM, ignitino back on, check for any voltage on ckt 496 (diagram will help find it!) If there is any voltage there, ckt 496 is shorted to another voltage supply. If no voltage is there, one or both of the knock sensors are inop or improperly installed or the module is inop or the PCM is inop.
IF: only one of the sensor's leads has 5 volts, then there is an open wire on its splice. (Both knock sensors are on the same circuit from the module and they are spliced off like a Y)
IF: neither sensor's lead has 5 volts, then there is an open or ground issue between the splice and the PCM or the module or PCM is inop.
Also, check the routing of the wires to the knock sensors. If they come too close to a spark plug wire, the spark can induce a current in the KS circuit and also throw code 43.
Circuit 496 is the line from the KS module to the sensors and is a dark blue wire.
Post up what you find!
Knock sensors can be destroyed by over torquing. Use 14 foot pounds if you wind up replacing the sensors. You probably know this already but they go through the water jackets so a coolant drain is in order when replacing them.
Here's how it works...The sensors should have a constant supply of 5 volts. They contain little crystals that generate an AC signal that rides on the same circuit and when there are no knocks they birng the circuit down to about 1.5 volts. The module listens for that AC signal and when it hears a strong one, it sends a knock event to the PCM which records a knock. Too many knocks in one time frame and the PCM retards ignition timing.
Ok so with the key on "run", engine off, check both terminals in the wire to the knock sensors one for each sensor both sensors for +5 volts to ground.
IF:
Both at 5 volts, check resistance between knock sensor's terminal and ground you should have 3,300-4,500 Ohms. If not replace the sensor that didn't have the correct resistance. If both have the proper resistance, ignition off, disconnect connector D from the PCM, ignitino back on, check for any voltage on ckt 496 (diagram will help find it!) If there is any voltage there, ckt 496 is shorted to another voltage supply. If no voltage is there, one or both of the knock sensors are inop or improperly installed or the module is inop or the PCM is inop.
IF: only one of the sensor's leads has 5 volts, then there is an open wire on its splice. (Both knock sensors are on the same circuit from the module and they are spliced off like a Y)
IF: neither sensor's lead has 5 volts, then there is an open or ground issue between the splice and the PCM or the module or PCM is inop.
Also, check the routing of the wires to the knock sensors. If they come too close to a spark plug wire, the spark can induce a current in the KS circuit and also throw code 43.
Circuit 496 is the line from the KS module to the sensors and is a dark blue wire.
Post up what you find!
Wow thanks!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by jakers
One thing I am thinking about is that I wass running low on fuel one afternoon and ended up buying some mid-grade gas (89 octane) because the station was out of the 91+ Octane stuff.
RACE ON!!!
