2003 4.6 EGR help
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1st Gear
Joined: Jul 2024
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2003 4.6 EGR help
Truck threw code 401. Cleaned throttle body thoroughly. Reset code. No code couple days. Threw code 401 again.
Replaced EGR valve. Threw same code ten minutes later.
Replaced EGR valve pressure sensor because the ends broke off when trying to remove vacuum lines. Deleted code. Same p401 code ten minutes later.
Tried to remove EGR vacuum reservoir. Vacuum nipple broke. Replaced. Reset code. Code threw again.
Have power to positive side of vacuum reservoir. Originally no ground to PCM on vacuum reservoir.
Disconnected PCM. Inserted probe to pin 47 that goes to ground on vacuum reservoir. Across voltmeter leads get .1ohm resistance. From pcm to vacuum reservoir ground pin I get 1.3 ohm.
Reconnected PCM, left probe at PCM. At PCM I had ground at pin 47 both key off and key on(12v pos from battery).
Started truck. Hooked positive battery to negative on vacuum reservoir solenoid. Showed .196vdc. then negative battery to positive on vacuum reservoir solenoid, got full 13.6v.
I have low vacuum at EGR. Not strong like at EGR vacuum reservoir solenoid.
Unsure next step in troubleshooting.
Any help appreciated.
Replaced EGR valve. Threw same code ten minutes later.
Replaced EGR valve pressure sensor because the ends broke off when trying to remove vacuum lines. Deleted code. Same p401 code ten minutes later.
Tried to remove EGR vacuum reservoir. Vacuum nipple broke. Replaced. Reset code. Code threw again.
Have power to positive side of vacuum reservoir. Originally no ground to PCM on vacuum reservoir.
Disconnected PCM. Inserted probe to pin 47 that goes to ground on vacuum reservoir. Across voltmeter leads get .1ohm resistance. From pcm to vacuum reservoir ground pin I get 1.3 ohm.
Reconnected PCM, left probe at PCM. At PCM I had ground at pin 47 both key off and key on(12v pos from battery).
Started truck. Hooked positive battery to negative on vacuum reservoir solenoid. Showed .196vdc. then negative battery to positive on vacuum reservoir solenoid, got full 13.6v.
I have low vacuum at EGR. Not strong like at EGR vacuum reservoir solenoid.
Unsure next step in troubleshooting.
Any help appreciated.
Lead Driver
Joined: Nov 2020
Posts: 7,128
Likes: 1,945
From: Sportsman's Paradise
Truck threw code 401. Cleaned throttle body thoroughly. Reset code. No code couple days. Threw code 401 again.
Replaced EGR valve. Threw same code ten minutes later.
Replaced EGR valve pressure sensor because the ends broke off when trying to remove vacuum lines. Deleted code. Same p401 code ten minutes later.
Tried to remove EGR vacuum reservoir. Vacuum nipple broke. Replaced. Reset code. Code threw again.
Have power to positive side of vacuum reservoir. Originally no ground to PCM on vacuum reservoir.
Disconnected PCM. Inserted probe to pin 47 that goes to ground on vacuum reservoir. Across voltmeter leads get .1ohm resistance. From pcm to vacuum reservoir ground pin I get 1.3 ohm.
Reconnected PCM, left probe at PCM. At PCM I had ground at pin 47 both key off and key on(12v pos from battery).
Started truck. Hooked positive battery to negative on vacuum reservoir solenoid. Showed .196vdc. then negative battery to positive on vacuum reservoir solenoid, got full 13.6v.
I have low vacuum at EGR. Not strong like at EGR vacuum reservoir solenoid.
Unsure next step in troubleshooting.
Any help appreciated.
Replaced EGR valve. Threw same code ten minutes later.
Replaced EGR valve pressure sensor because the ends broke off when trying to remove vacuum lines. Deleted code. Same p401 code ten minutes later.
Tried to remove EGR vacuum reservoir. Vacuum nipple broke. Replaced. Reset code. Code threw again.
Have power to positive side of vacuum reservoir. Originally no ground to PCM on vacuum reservoir.
Disconnected PCM. Inserted probe to pin 47 that goes to ground on vacuum reservoir. Across voltmeter leads get .1ohm resistance. From pcm to vacuum reservoir ground pin I get 1.3 ohm.
Reconnected PCM, left probe at PCM. At PCM I had ground at pin 47 both key off and key on(12v pos from battery).
Started truck. Hooked positive battery to negative on vacuum reservoir solenoid. Showed .196vdc. then negative battery to positive on vacuum reservoir solenoid, got full 13.6v.
I have low vacuum at EGR. Not strong like at EGR vacuum reservoir solenoid.
Unsure next step in troubleshooting.
Any help appreciated.
Remove the throttle body where it bolts to the manifold and dig it out.
Low vacuum is expected at any speed other than above 35 or 40 mph.
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